and the solution is, that as I find this belief arising not from a single instance, but only from the constant
conjunction
of the two impressions, the liveliness must be due to custom, i.
Windelband - History of Philosophy
Cf.
also B.
Rlittenauer, Zur VorgescMchte des Idealism*!
und Kriticismus (Freiburg, 1882), and Geil, op.
cit.
, pp.
66 ft".
lb. IV. 2.
»Ib. II. 23,20; IV. 10. 9.
»1
8, 7
a
is,
Chap. 1, § 34. ] Knowledge of the Order World : Berkeley . 469
roent of the cogito ergo sum. This principle he carries over entirely from the metaphysical realm into that of empirical psychology. . . Self-certainty is for him thafr^jftne " internal sense " ; intuition in this case refers only to our states and activities, not to our essence ; it shows us, indeed, immediately and without doubt, that we are, but not what we are. The question a^ to the substance of the soul (and accordingly the question als»> As torts relation to the body) is as incapable of an answer as the question as to the " what" of any substance whatever.
Nevertheless, Locke holds it to be possible to gain a demonstrative certainty of the existence of Ood. For this purpose he adopts the first of the Cartesian proofs (cf. § 30, 5) in a somewhat modified form, and adds the ordinary cosmological argument An infinite, eternal, and perfect being must be thought, an ultimate cause of finite substances of which man intuitively knows himself to be one.
So manifold and full of contradictions are the motifs which cross in Locke's doctrine of knowledge. The exposition, apparently so easy and transparent, to which he diluted Cartesianism, glides over and away from the eddies which come up out of the dark depths of its historical presuppositions. But as the ambiguous, indeterminate nature of his psychology unfolded itself in the antithesis in the fol lowing developments, so, too, this episteinological metaphysics offered points of departure for the most varied transformations.
2. The very first of these shows an audacious energy of one-sided- ness in contrast with the indecisiveness of Locke. Berkeley brought the ascendeucy of inner experience to complete dominance by putting an end to the wavering position which Locke had taken upon the question as to the knowledge of bodies. This he did with the aid of his extreme Nominalism and with a return to the doctrines of Hobbes. He demolished the conception of corporeal substance. Ac cording to the distinction of primary and secondary qualities, it was held that a part of that complex of ideas which perception presents us as a body should be separated out, and another part retained as alone real; but this distinction, as Hobbes had already taught (cf. f 31, 2), is in the nature of the case erroneous. The "mathe matical " qualities of ladies are as truly ideas within us as the sense qualities, and Berkeley had demonstrated exactly this point with analogous arguments in his Theory of Vi»ion. He attacks the warrant of the distinction of Descartes (and of Democritus). But while, according to this view, all qualities of bodies without excep
tion are ideas in us, Locke has retained as their real supporter a superfluous unknowable "substance " ; in a similar way others speak of matter as the substrate of sensible qualities.
470 The Enlightenment : Theoretical Questions. [Part V.
But in all these cases, says Berkeley, it is demanded of us to regard an abstraction as the only actual reality. Abstract ideas, however, do not exist, — they do not exist even in the mind, to say nothing of existing in natura rerum. Locke was then quite right in saying that no one could know this "substance ": no one can even think it; it is a fiction of the schools. For the naive consciousness, for "common sense," whose cause Berkeley professes to maintain against the artificial subtlety of philosophers, bodies are just exactly what is perceived, no more and no less ; it is only the philosophers who 3eek for something else behind what is perceived, — something mysterious, abstract, of which they themselves cannot say what it is. For the unperverted mind, body is what one sees, touches, tastes, smells, and hears : its esse is percipi.
Body is then nothing but a complex of ideas. If we abstract from a cherry all the qualities which can be perceived through any of the senses, what is left ? Nothing. The idealism which sees in a body nothing farther than a bundle of ideas is the view of the common man ; it should be that of philosophers also. Bodies possess no other reality than that of being perceived. It is false to suppose that there is in addition to this a substance inherent within them, which "appears" in their qualities. They are nothing but the sum of these qualities.
In reply to the question that lies close at hand, in what the differ ence consists between the " real " or actual body and that which is only imagined or dreamed of, if all bodies are only perceived, Berkeley answers with a spiritualistic metaphysics. The ideas which constitute the existence of the outer world are activities of spirits. Of the two Cartesian worlds only one has substantial existence ; only the res cogitantes are real substances, the res extensa are their ideas. But to finite spirits the ideas are given, and the origin of all ideas is to be sought only in the infinite Spirit, in God. The reality of bodies consists, therefore, in this, that their ideas are
communicated by God to finite spirits, and the order of succession in which God habitually does this we call laws of Nature. Hence Bishop Berkeley finds no metaphysical difficulty in supposing that God under certain circumstances departs from the usual order for some especial end, and in this case man speaks of miracles. Ou the other hand, a body is unreal which is presented only in the indi vidual mind according to the mechanism of memory or imagination, and without being at the same time communicated to the mind by God. And finally, since the actual corporeal world is thus changed into a system of ideas willed by God, the purposiveness which its arrangement and the order of its changes exhibit gives rise to no further oroblem.
Chap. 1, § 34. ] Knowledge of the Outer World : Collier. 471
The parallelism between this inference from Locke and that which Malebranche had drawn from Descartes is unmistakable ; and Malebranche and Berkeley are also at one in holding that God alone is the active force in the world, and that no individual thing is efficiently operative (cf. § 31, 8). It is extremely interesting to see how the extreme Realism of the Frenchman and the extreme Nominalism of the Englishman amount to the same thing. The grounds on which the views are based could not be more different : the result is the same. For what still separated the two could be easily removed out of the way. This was proved by a contemporary and countryman of Berkeley's, Arthur Collier (1680-1732) in his interesting treatise Clavis Universalis. 1 Malebranche,1 indeed, as a Cartesian, had not directly demurred to the reality of the corporeal world, but had held that we could understand the knowledge of this world by man, only on the hypothesis that the ideas of bodies in God are the common original, in accordance with which God pro duces, on the one hand, the actual bodies, and, on the other, the
ideas of these bodies in finite minds. Collier showed now that in this theory the reality of the corporeal world played a completely superfluous rSle : since no actual relation between the corporeal world and human ideas is assumed, the value of human ideas for knowledge remains quite the same if we posit only an ideal cor poreal world in God, and regard this as the real object of human knowledge.
The idealism, which proceeded in this way from the cogito ergo turn along several paths, was attended by still another paradox as a by-product, which is occasionally mentioned in the literature of the eighteenth century without any definite name or form. Each individual mind has certain, intuitive knowledge only of itself and of its states, nor does it know anything of other minds
through ideas, which refer primarily to bodies and by an argument from analogy are interpreted to indicate minds. If, however, the whole corporeal world is only an idea in the mind, every individual is ultimately certain only of his own existence ; the reality of all else, all other minds not excluded, is problematical and cannot be demonstrated. This doctrine was at that time designated as Egoism, now it is usually called Solipsism. It is a metaphysical
1 The alternative title of the book reads, A Xev> Inquiry after Trvth. being m Demonstration of the Son-Existence or Impossibility of an External World
It wwi edited together with Berkeley's treat in* in the (iennan •• Collection of the Principal Writings which deny the Reality of their oxen Body ( . '. ') and of the tehole Corporeal World," by Kechenbach (Koitock. 1766).
* Wh<>«e doctrine had become known in England by the agency especially of John Sorris (Essai (Tun Theorie du Monde Idial, Lond. 1704).
(Lond. 1123).
except
472 Tlit EnliyhteniHtnt : Theoretical Questions. [Part V
sport which must be left to the taste of the individual; for the solipsist refutes himself by beginning to prove his doctrine to others.
Thus, following in the train of the Meditations, in which Descartes recognised self-consciousness as the rescuing rock in the sea of doubt, the result was finally reached which Kant later characterised as a scandal to philosophy ; namely, that a proof was demanded for the reality of the outer world, and none adequate could be found. The French materialists declared that Berkeley's doctrine was an insane delusion, but was irrefutable.
3. The transformation of Locke's doctrine by Berkeley leads farther in a direct line to Hume's theory of knowledge. To the nominalistic denial of abstract ideas the penetrative and profound Scot attached his distinction of all intellectual functions into im pressions, and ideas which are copies of impressions ; and coincident with his distinction is that of intuitive and demonstrative knowl edge. Each kind of knowledge has its own kind of certainty. Intuitive knowledge consists simply in the affirmation of actually present impressions. What impressions I have, I can declare with absolute certainty. I can make no mistake in this, in so far as I keep within the bounds of simply stating that I have a perception possessing this or that simple or complex content, without adding any conceptions which would put any interpretation upon this content.
As among the most important of these impressions which have immediate intuitive certainty Hume reckons the relations in space and time of the contents of sensation, — the fixing of the co-exist ence or succession of elementary impressions. The spatial order in which the contents of perception present themselves is undoubtedly given immediately with the contents themselves, and we likewise possess a sure impression as to whether the different contents are perceived at the same time or in succession. Contiguity in space and time is therefore intuitively given together with the impres sions, and of these facts the human mind possesses a knowledge which is perfectly certain and in nowise to be questioned. Only,
in characterising Hume's doctrine, it must not be forgotten that this absolutely certain matter-of-fact quality, which belongs to impressions, is solely that of their presence as mental states. In this meaning and restriction intuitive knowledge embraces not only the facts of inner experience, but also those of outer experience, but at the price of recognising that the latter are properly only species of the former, — a knowledge, that of mental states.
Contiguity in space and time however, but the most elementary
is,
is,
Chap. J, $ 34. ] Knowledge of the Outer World: Hume. 478
form of association between perceptions ; besides this Hume reckons two other laws, those of resemblance (or contrast, respectively) and causality. As regards the former of these two forms of relation, we hare a clear and distinct impression of the likeness or unlike- ness of sensations, and of the different degrees of these ; it consists in the knowledge of the degree of resemblance in our own (sensi tive) action, and belongs therefore to the impressions of the inner sense, which Locke called reflection. On this is based, consequently, a demonstrative knowledge of complete certainty ; it concerns the forms of that comparison between magnitudes which we perform upon the given contents of our ideas, and is nothing but an analysis of the regularity with which this takes place. This demonstrative science is mathematics ; it develops the laws of equality and propor tion with reference to numbers and space, and Hume is inclined to concede a still higher epistemological value to arithmetic than to geometry. 1
4. But mathematics is also the sole demonstrative science; and is that just because it relates to nothing else than the possible rela tions between contents of ideas, and asserts nothing whatever as to any relation of these to a real world. In this way the terministic principle of Hobbes (cf. § 30, 3) is in complete control with Hume, but the latter proceeds still more consistently with his limitation of this theory to pure mathematics. Fo»Hume declares that no asser tion respecting the external world is capable of demonstration ; all our knowledge is limited to the ascertaining and verifying of
impressions, other.
and to the relations of these mental states to each
Hence it seems to Hume an unauthorised trenching of thought beyond its own territory, when the resemblance between ideas is interpreted as meaning metaphysical identity ; this is the case in
every employment of the conception of substance. Whence is this conception ? It is not perceived, it is not found as a content either in particular sensations or in their relations; substance is the unknown, indescribable support of the known contents of ideas. Whence this idea for which no impression is to be found in the whole circuit of sensations as its necessary original ? Its origin is to be sought in reflection. It is the copy of a frequei tly repeated
conjunction of ideas. By the repeated being together of impres sions, by the custom of the like ideational process there arises by virtue of the law of association of ideas the necessity of the idea of their co-existence, and the feeling of this associative necessity of the
' Treat. I. 2, 1 ; I. 3, 1.
474 The Enlightenment : Theoretical Questions. [Part V.
ideational process is thought as a real belonging together of the elements of association, i. e. as substance.
The thought-form of inherence is thus psychologically explained, and at the same time epistemologically rejected; nothing corre sponds to it further than the feeling of a likeness in the ideational conjunction ; and since we can never know anything of existence except by immediate sense-perception, the Reality of the idea of substance is incapable of proof. It is clear that Hume thus makes Berkeley's doctrine his own, so far as it concerns corporeal things.
But Berkeley had but half done his work upon the idea of substance. He found that bodies are only complexes of sensations ; that their being is identical with their being perceived ; that there is no sense or meaning in hypostatising their belonging together, as an unknown substance : but he let the psychical substances, spirits, the res cogi- tantes, stand ; he regarded them as the supports or agents in which all these ideational activities inhere. Hume's argument applies to this latter class also. What Berkeley showed of the cherry is true also of the " self. " Inner perception, also (such was the form which it had actually taken on already with Locke; cf. above, No. 1), shows only activities, states, qualities. Take these away, and noth ing remains of Descartes' res cogiians either : only the " custom " of constant conjunction of ideas in imagination is at the basis of the conception of a "mind"; the self is only a " bundle of perceptions. " '
The same consideration holds also, mxttatis mutandis, for causality, that form under which the necessary connection between contents of ideas is usually thought : but this is neither intuitively nor de monstratively certain. The relation of cause and effect is not per ceived ; all that we can perceive by the senses is the relation in time, according to which one regularly follows the other. If, now, thought interprets this sequence into a consequence, this post hoc into a propter hoc,1 this too has no basis in the content of the ideas causally related to each other. From a "cause" it is not possible to deduce logically its " effect " ; the idea of an effect does not con tain within it that of its cause. It is not possible to understand the causal relation analytically. ' Its explanation is, according to
1 Treat. I. , Part IV. The objectionable consequences ■which resulted from this for religious metaphysics perhaps occasioned Hume, when working over his Treatise into the Essays, to let drop this which cut most deeply of all his investigations.
2 In this respect Hume had a forerunner in his countryman Joseph Glanril (1636-1680), who combated the mechanical natural philosophy from the stand point of orthodox scepticism in his Scepsis Scientifica, 1665.
* The same thought lay already at the basis of the Occasionalistic meta physics (cf. § 31, 7); for the essential reason for its taking refuge in mediation by the will of God was the logical incomprehensibility of the causal relation.
Chap. 1, $ 34. ] Knowledge of the Outer World : Hume. 47?
Hume, to be gained by means of association of ideas. Through the repetition of the same succession of ideas, and the custom of finding them follow each other, an inner necessity or compulsion arises of imagining and expecting the second after the first ; and the feeling of this inner necessity with which one idea calls up another is inter preted as a real objective necessity, as if the object corresponding to the first idea forced that corresponding to the other to a real existence in natura rerum. The impression in this case [of which the idea of cause and effect is a copy] is the necessary relation between the ideational activities [activities of the "imagination"], and from this arises, in the idea of causality, the idea of a neces sary relation between the ideational contents [i. e. that A. causes 8 ; whereas the case really is that the idea of A causes the idea of B, i. e. recalls it by the law of association].
[In view of the extreme condensation of the above statement, a fuller outline of Hume's discussion of causality may be useful. As found in the Treatise it is briefly as follows: All knowledge as to matters of fact ("probability"), if it goes beyond the bare present sensation, depends on causation. Tins contains three essential elements, — contiguity, succession, and necessary connection. We can explain the first two (i. e. can find the impression from which they come), but no impression of sensation can be fountt for the third and most impor tant. To aid in the search for its origin we examine the principle both in its general form and in its particular application, asking (1), why we say that whatever begins to exist must have a cause, and (2), why we conclude that a particular cause must necessarily have a particular effect.
(1) Kxamination of the first gives the negative result that the principle is not intuitively or demonstratively certain (the opposite is not inconceivable), hence it is not derived purely a priori, i. e. by analysing relations between ideas ; therefore it must be from experience. — (2) But hoic from experience? Taking for convenience the second question stated above, the particular instead of the general, it is evident (a) that the senses cannot tell that a particular effect will follow a given cause ; they are limited to the present. Nor (6) can such knowl edge as to future events be gained by reasoning on experience, as this would involve knowing that Instances of which we have had no experience must resemble those of which we had experience (would assume the uniformity of Nature), (e) Therefore the principle apparently must come from the only remaining faculty, imagination. This seems at first Impossible, in view of the strong belief which attaches to these ideas (e. g. that fire will burn), in contra
distinction from ordinary ideas of fancy. The question as thus shifted now becomes: (3) Hine explain the fact that )ce believe that a particular effect will follow a given cause ? The only difference between the ideas of the senses and memory (in which we believe) and those of fancy (in which we do not) is that of the feeling joined with them. The ideas of memory are more strong and
The same was also recognised by Kant In his "Attempt to introduce the Concep tion of Segatite Quantities into Philosophy " (cf. the general remark at the close) in a manner essentially in agreement with Hume. And finally. Thomas Urotrn ( On Cause and Effect), who also is not disinclined to Occasionalism (cf. op. eft. , pp. 106 ff. ), in a very interesting way deduces psychologically, and at the same time rejects epistemolngically (ib. 184 ff. ), the demand for an "explaining" or "understanding" of the actual succession of facts in time. Perception shows causes and effects roughly. The explanation of the process consists, then, in it* analysis into particular, simple and elementary causal relations. By this means the illusion arise* as if these latter must be yet again made analytically com- piwhmaibie.
476 The Enlightenment : Theoretical Questions. [Pakt V
lively. Hence the problem is, What makes the idea (e. g. that fire will burn } so " lively " that I believe in it ?
and the solution is, that as I find this belief arising not from a single instance, but only from the constant conjunction of the two impressions, the liveliness must be due to custom, i. e. to the habitual association of the ideas. " All probable reasoning is nothing but a species of sensation. "
This same doctrine explains the origin of the idea of necessary connection. For this does not arise from one instance, but from several. Bepetition dis covers nothing new, nor does it produce anything new in the objects, but it does produce something in the mind, viz. a determination to pass from one object to its usual attendant. 'I lie idea of necessity must arise from some impression. There is no external impression that can give rise to hence must be an im pression of reflection, and the only one available that propensity which custom produces to pass from an object to the idea of its usual attendant. Xecessity something that exists in the mind, not in objects. This confirmed by compar ative psychology (animals infer from experience through custom), by the theory of probabilities, and (in the Inquiry) by the freedom of the will, since belief may be reached in all these without necessarily holding to any objective neces sary connection. — Tr. ]
In this way, Hume's theory of knowledge disintegrates the two fundamental conceptions about which the metaphysical movement of the seventeenth century had revolved. Substance and causality are relations between ideas, and cannot be proved or substantiated either by experience or by logical thought: they rest upon the fictitious substitution of impressions derived from reflection, for those of sensation. But with this, the ground completely taken from under the feet of the ordinary metaphysics, and in its place appears only epistemology. The metaphysics of things gives place to metaphysics of knowledge.
Hume's contemporaries characterised this result of his investi gations — especially out of regard for its consequences with respect
to religious metaphysics (cf. 35, — as Scepticism yet essentially different from those doctrines to which this name his torically belongs. The settling of facts by sense-experience is, for Hume, intuitive certainty mathematical relations pass for demon strative certainty but, as for all alleged assertions by means of conceptions ["by abstract reasoning"] with reference to a reality other than that belonging to ideas concerning matter of fact and
Hume cries, "Into the fire with it! " There no knowledge of what things are and how they work we can say only what we perceive by sensation, what arrangement in space and time and what relations of resemblance we experience between them. This doctrine absolutely consistent and honest empiricism: demands that the only source of knowledge perception, nothing further shall be mingled with this than what actually contains. With this, all theory, all examination of cause, all doctrine of the " true Being" behind "phenomena" excluded. 1 If we characterise
existence"],
Berkeley is, therefore, correctly understood only from the point of view of
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Chap. 1, § 34. ] Knowledge of the Outer World : Hume. 477
this standpoint as Positivism, in accordance with the terminology of our century, we may say that its systematic basis was established by Hume.
But England's deepest thinker gave to this radical theory of knowledge a characteristic supplement. The associations of ideas which lie at the basis of the conceptions of substance and causality are, indeed, attended by neither intuitive nor demonstrative certainty; instead of this, however, they are accompanied by a conviction which has its roots in feeling, a natural belief, which, unper verted by any theoretical reflections, asserts itself victoriously in man's practical procedures, and is completely adequate for the attainable ends of life and for the knowledge relating to these. On this rests the experience of daily life. To question this never came into Hume's mind : he only wishes to prevent this from playing the role of an experimental science, for which it is inadequate. With the entire earnestness of philosophical depth he unites an open vision for the needs of practical life.
7. For the reception of this positivism the intellectual temper was less favourable in England than in France. Here the renuncia tion of any attempt at a metaphysics of things lay already prepared in the fundamental sceptical tendency which had made its appear ance so repeatedly from the Cartesian philosophy ; and the preva lence of this temper had been especially furthered by Bayle, whose criticism was, indeed, in principle directed chiefly against the rational grounding of religious truths ; but at the same time applied to all knowledge reaching beyond the sensuous, and therefore to all meta physics. Besides this, there was in the French literature a freer tendency that belongs to men of the world, which had likewise been furthered by Bayle, and at the same time by the influence of Eng lishmen, — a tendency which would strip off the fetters of the system of the schools, and demanded the immediate reality of life instead of abstract conceptions. Thus Bacon's doctrine, with its limitation of science to physical and anthropological experience, became more rffirarious in France than in his own home. The " point de systeme " meets us here at"every step; no one any longer wishes to know
anything of the causes premieres," and this Baconian platform with all its encyclopaedic and programmatic extension was laid down by rTAlembert as the philosophical basis of the Encyclopaedia. *
Hume : his idealism to half positivism. He lays especial weight upon the point that behind the ideas of bodies we are not still to seek for something abstract, •omethlng existent in itself. If this principle be extended to minds, we have
Hume's doctrine ; for with the fall of Berkeley's spiritualistic metaphysics, the order of phenomena willed by (iod. to which he had reduced causality, falls also.
1 In the Ditcours Prtlimiiiairr.
478 The Enlightenment : Theoretical Questions. [Part V.
In Germany the Wolffian system was opposed with the "point de systeme " by men like Crousaz and Maupertuis on grounds of taste, and, in fact, the pedantry of this text-book philosophy offered many points of attack. In contrast with this the German Popular Philos ophy prided itself upon its absence of system ; as developed by Mendelssohn it would refrain from all subtleties as to that which cannot be experienced, and employ itself the more with that which is useful for men. And, lastly, we find a fine example of harmony with this temper in Kant's Dreams of a Ghost-Seer, where he lashes the architects of various artificial worlds of thought with sharp irony, and pours out copious scorn upon metaphysical endeavour with a gallows-humour which touches his own inclination in a most sensitive point. Among the German poets Wieland is in this same spirit the witty anti-metaphysician.
8. A very peculiar turn was taken by positivism, finally, in the later doctrine of Condillac. In him converge the lines of the French and the English Enlightenment, and he finds a positivistic synthesis of sensualism and rationalism, which may be regarded as the most perfect expression of modern terminism. His Logic l and his post humous Langue des Calculs developed this doctrine. It is built up essentially upon a theory of " signs " (signes). 2 Human ideas are all of them sensations, or transformations of such, and for these no especial powers of the soul are needed. 3 All knowledge consists in the consciousness of the relations of ideas, and the fundamental relation is that of equality. The business of thinking is only to bring out the relations of equality between ideas. 4 This is done by analysing the complexes of ideas into their constituent elements and then putting them together again: dicomposition des pMno- menes and composition des idles. The isolation of the constituent elements which is requisite for this can, however, be effected only with the aid of signs or language. All language is a method for the analysis of phenomena, and every such method is a "language. " The different kinds of signs give different "dialects" of the human language: as such Condillac distinguishes five, — the fingers (ges tures), sound-language, numbers, letters, and the signs of the infini tesimal calculus. Logic, as the universal grammar of all these
* This Condillac maintains against Locke, and indeed already in his TraiU des Sensations, and his school do the same against the Scots.
4 In these determinations lie suggestions from Hobbes as well as from Hume.
1 A text-book for " Polish professors. "
J After the Langue des Calculs became known, the Institute of Paris and the Berlin Academy gave out, almost at the same time, the theory of signs as the subject for. their prizes. At both places a great number of elaborations were presented, mostly of very inferior value.
Chap. 1, § 34. ] Knowledge of the Outer World : Condtllae. 479
languages, determines, therefore, mathematics also, and indeed the higher as well as the elementary, as special cases.
All science thus contains only transformations. The thing to be done is always to make out that the unknown, which one is seeking, is really something already known; that to find the equation which shall put the unknown x equal to composition of ideas
just for this end that the structures of perception must be
It evident that this but a new generalising mode of expression for Galileo's doctrine of the method of resolution and composition; but rises here upon purely sensualistic basis denies the constructive element which Hobbes
had so sharply emphasised and makes of thinking reckoning with only given quantities. In doing this rejects all thought of relation of these data to metaphysical reality, and sees in scientific knowledge only a structure built up of equations between contents of ideas in accordance with the principle mime est mtme. The human world of ideas completely isolated within itself, and truth cunsists only in the equations that can be expressed within this world by " signs. "
9. Indifferent as this Ideology professed to be metaphysically, its sensualistic basis, nevertheless, involved a materialistic metaphysics. Even though nothing was to be said as to the reality corresponding to sensations, there still remained in the background the popular idea that sensations are produced by bodies. On this account the cautious restraint that belonged to these positivistic consequences of sensualism needed only to be neglected to convert the anthropo logical materialism, which had developed in the psychological theories, into metaphysical and dogmatic materialism. And so Lamettrie spoke out with coquettish recklessness what many others
did not dare to confess to themselves, to say nothing of confessing or defending openly.
But other lines of thought in natural science, independently of ideology, were also driving toward materialism. Lamettrie had very rightly seen that the principle of the mechanical explanation
of Nature would ultimately tolerate nothing in addition to matter moved by its own forces long before Laplace gave the well-known answer that he did not need the " hypothesis of the deity " French natural philosophy had attained this standpoint. That the world of gravitation lives in itself was Newton's opinion also; but he believed that the first impulse for its motions must be sought in an action of God. Kant went step farther when he cried in his Natural History of the Heavens, "Give me matter, and will build
yoa a world. " He pledged himself to explain the whole universe
previously decomposed.
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480 Tlie Enlightenment : Theoretical Questions. [Part \
of the fixed stars after the analogy of the planetary system,1 and traced the origination of the individual heavenly bodies out of a fiery-fluid primitive condition solely to the opposed working of tbi two fundamental forces of matter, attraction and repulsion. But Kant was convinced that the explanation which is sufficient for solar systems shatters when applied to the blade of grass and the caterpillar ; the organism seems to him to be a miracle ( Wunder) in the world of mechanics.
The French philosophy of Nature sought to overcome this obstacle also, and to put the problem of organisation out of the world. Among the countless atom-complexes, it taught, there are also those which
the capacity of preserving and propagating themselves. Buffon, who pronounced and carried through with full energy this frequently expressed thought, gave to such atom-complexes the name organic molecules, and by assuming this conception all organic life might be regarded in principle as an activity of such molecules, which develops according to mechanical laws, in contact with the external world. 8 This had been already done by Spinoza, of whose theory of Nature Buffon frequently reminds us ; the latter, also, speaks of God and " Nature " as synonyms. This naturalism found in mechanics, accordingly, the common principle for all corporeal occurrence. But if now ideology taught that ideas and their transformations should be regarded as functions of organisms, if it no longer was regarded as impossible, but more and more seemed probable, that the thing which thinks is the same that is extended and moves, if Hartley and Priestley in England and Lamettrie in France showed that a change in consciousness is a function of the nervous system, — it was but a step from this to teach that ideas with all their transformations form only a special case of the mechanical activity of matter, only a particular kind of its forms of motion. While Voltaire had expressed the opinion that motion and sensation
might perhaps be attributes of the same unknown substance, this hylozoism changed suddenly into decided materialism as soon as the dependence of the psychical upon the physical was given the new interpretation of a likeness in kind between the two, and it is often only by soft and fine shades of expression that the one is
>The suggestion for this brilliant astro-physical hypothesis, to which Lam bert also came very near in his Kosmologischen Briefen, and which was devel oped later in a similar manner by Laplace, was due perhaps to a remark by
Buffon. Cf. O. Liebmann, Zur Analysis der Wirklichleeit, 2d ed. , p. 376.
2 This principle of Buffon was further developed later by Lamarck (Philoso-
phie Zoologique, Paris, 1809), who attempted to explain the transformation of organisms from the lower to the higher forms by a mechanical influence of the outer world, by adaptation to the environment-
possess
Chap. 1, { 34. ] Knowledge of the Outer World : Materialism. 481
converted into the other. This transition is presented in the writings of Robinet. He gives a metaphysical flight to the philos ophy of Nature. Finding support in the development system of the Leibnizian Monadology, he regards the graded scale of things as an infinite multiplicity of forms of existence, in which the two factors of corporeality and psychical function are mixed in all the different relations possible, so that the more the nature of a particular thing unfolds in the one direction, the less is its activity in the other. This holds true, also, according to Robinet, in the case of the vital movements of individual creatures ; the force which they use men tally is lost physically, and conversely. Regarded as a whole, however, the psychical life appears as a special form which the fundamental material activity of things is able to assume, to be later translated back again into its original form. Robinet thus regards ideas and activities of the will as mechanical transformations of the nervous activity which can be changed back again into that. Noth ing takes place psychically which was not predisposed in the physi cal form ; and the body, accordingly, receives in psychical impulses only the reaction of its own motion.
In the Systeme de la Nature materialism appears at last undis guised as a purely dogmatic metaphysics. It introduces itself with the Epicurean motive of wishing to free man from fear of the super- sensuous. It shall be shown that the supersensuous is only the invisible form of activity of the sensuous. No one has ever been able to think out anything of a supersensuous character that was not a faded after-image of the material. He who talks of idea and will, of soul and God, thinks of nervous activity, of his body and the world over again in an abstract form. For the rest, this " Bible of Materialism" presents no new doctrines or arguments in its pain fully instructive and systematically tedious exposition : yet a certain weight in its conception taken as a whole, a greatness of stroke in drawing the lines of its Weltanschauung, a harsh earnestness of pre sentation, is not to be mistaken. This is no longer a piquant play
of thoughts, but a heavy armed attack upon all belief in the imma terial world.
10. In spite of psycho-genetic opposition, the problem of knowl edge as conceived by the supporters of " innate ideas " was not all too unlike the view which obtained with the sensualists. The dual- istic presupposition assumed by both classes made it difficult for the latter to understand the conformity which the ideas called out in the mind by bodies bear to the bodies themselves. But it seemed almost more difficult still to understand that the mind should cog nise a world independent of by means of the development of the
it,
482 The Enlightenment : Theoretical Questions. [Part V.
thought-forms which are grounded in its own nature. And yet exactly this is an assumption so deeply rooted in human thought, that it passes for the most part as self-evident and a matter of course, not only for the naive consciousness, but also for philo sophical reflection. It was the mission of the Terminism, whose after-workings were active in modern philosophy, to shake this fun damental dogmatic conviction, and push forward for consideration the question as to the ground of that conformity between necessity of thought, on the one hand, and reality on the other. Even Des cartes had found it necessary to support the knowing power of the lumen naturale by the veroxitas dei, and thereby had shown the only way which the metaphysical solution of the problem could take.
To be sure, where that philosophical impulse was lacking which directs its 0aiyia£«v — its wonder — upon just that which is appar ently self-evident and a matter of course, the difficulty just men tioned weighed less heavily. This was the case with Wolff, in spite of all his power of logical clearness and systematic care, and with the Scots, in spite of all their fineness of psychological analysis. The former proceeds to deduce, more yeometrico, an extensive ontol ogy, and a metaphysics with its parts relating to God, to the world, and to the soul, all from the most general formal laws of logic, — from the principle of contradiction and that of sufficient reason (and this second principle is even to be reduced to the first). Wolff, indeed, stands so completely within the bounds of this logical schematism that the question never seems to occur to him at all, whether his whole undertaking — namely, that of spinning "a sci ence of all that is possible, in so far as it is possible " out of logical propositions — is authorised in the nature of the case. This problem was concealed for him the more as he confirmed every rational science by an empirical science [e. g. Rational by Empirical Psychol ogy, etc. ], — an agreement, indeed, which was possible only because his a priori construction of metaphysical disciplines borrowed from
experience step by step, though the loan was unnoticed. Neverthe less, this system, which was blessed with so many disciples, had the great didactic value of setting up and naturalising strictness in thought, clearness of conceptions, and thoroughness in proof, as the supreme rules for science, and the pedantry which unavoidably stole in with these found a sufficient counterpoise in other intellectual forces.
The Scottish philosophy contented itself with seeking out the principles of sound common sense. Every sensation is the sign — Reid too, thinks as terministically as this — of the presence of an object; thinking guarantees the reality of the subject; whatever
Chap. 1, § 34. ] Knowledge of the Outer World : Leibniz. 483
actually comes into being must have a cause, etc. Such principles are absolutely certain; to deny them or even to doubt them is absurd. This is especially true, also, of the principle that what the understanding recognises clearly and distinctly is necessarily so.
In this is formulated the general principle of a philosophical atti tude which is called dogmatism (after Kant), unconditional confi dence in the agreement of thought with reality. The above examples of the particular principles show how eclectically this common sense sought to gather its fundamental truths from the different systems of philosophy. In this respect the " gesunde Menschen verstand "
[sound common sense] of the German popular philosophers was entirely in accord with it. Mendelssohn, like Reid, was of the opinion that all extremes in philosophy were errors, and that the truth lay in the mean position : every radical view has a germ of truth which has been forced artificially to a one-sided and diseased development A sound, healthy thinking (Nicolai, especially, lays weight on this predicate) does justice to all the different motives and so finds as its philosophy — the opinion of the average man.
11. In the mind of Leibniz the problem was solved by the hypothesis of the pre-established harmony. The monad knows the world because it is the world: the content which it represents is from the beginning the universe, and the law of the monad's activity is the law of the world. On account of its " having no windows " it has no experience at all in the proper sense: nevertheless the possibility of knowing the world is so established in its very essence that all its states must be regarded as just such a knowledge. There is, accordingly, no difference between intellect and sensibility, either
as regards the objects to which they refer, or as regards the way in which consciousness relates itself to these objects : the only differ ence is that sensibility cognises the indistinct phenomenal form, while intellect cognises the true essence of things. From a scientific point of view, therefore, knowledge by the senses was treated partly as the imperfect, preliminary stage, partly as the indistinct anti-type for the intellect's insight : the " historical " sciences were regarded either as preparations for the philosophical, or as lower appendages.
From this relation a ]>eculiar consequence resulted. The sensuous niode of representation, too, has a certain peculiar perfection of its own, which differs from the clearness and distinctness of intellectual knowledge in apprehending the phenomenal form of its object with out any consciousness of grounds or reasons : and in this perfection, characteristic of sensuous knowledge, Leibniz , had set the feeling oj
> Cf. esp. Princ. dt la Sat. etdela Grace, 17.
484 The Enlightenment: Theoretical Quettiont. [Part V.
the beautiful. When, now, one of Wolff's disciples, Alexander Baum-
in whom the architectonic impulse toward systeinatisation was developed to a particularly high degree, wished to place by the side of logic as the science of the perfect use of the intellect, a corre sponding science of the perfection of sensation, an aesthetics, this dis cipline took on the form of a science of the beautiful. 1 Thus aesthetics,* as a branch of philosophical knowledge, grew up, not out of interest in its subject-matter, but with a decided depreciation of it ; and as a " step-sister " [lit. posthumous : nachgeborene Schwester'] of logic she was treated by the latter with very little understanding for her own peculiar nature, and with a cool intellectual pedantry. Moreover, this last-named rationalist, who followed Leibniz in regarding the actual world as the best, and therefore, as the most beautiful among all possible worlds, could set up no other principle for the theory of art than the sensualistic one of imitating Nature, and developed this principle essentially into a tedious poetics. But in spite of this, it remains Baumgarten's great service to have treated the beautiful again, and for the first time in modern philosophy, in a systematic way from the general conceptions of philosophy, and by so doing to have founded a discipline that was destined to play so important a part in the further development of philosophy, especially in that of Germany.
12. The Leibnizo-Wolffian conception of the relation between sense and understanding, and especially the geometrical viethod introduced for rational knowledge, encountered numerous opponents in the German philosophy of the eighteenth century, whose opposi tion proceeded not only from the incitements of English and French sensualism and empiricism, but from independent investigations as to the methodical and epistemological relation between mathematics and
philosophy.
In this latter line Rudiger, and, stimulated by him, Crusius, con
tended most successfully against the Wolffian doctrine. In oppos; tion to Wolff's definition of philosophy as the science of the possible, Rudiger asserted that its task is to know the actual. Mathematics, and, therefore, also a philosophy which imitates the methods of mathematics, have to do only with the possible, with the contradic- tionless agreement of ideas with one another ; a true philosophy needs the real relation of its conceptions to the actual, and such a
gotten,
1 Cf. H. Lotze, Gesch. der Aesthetik in Deutschland (Munich, 1868).
2 The name " aesthetics " was then adopted at a later time by Kant, after some resistance at first, for the designation of the philosophical doctrine of the beautiful and of art, and from him passed over to Schiller, and through the latter' s writings into general use.
Chat. 1, § 34. ] Knowledge of the Outer World: Kant. 485
relation is to be gained only by perception. Crusius made this point of view his own ; and although he thought in a less sensual ist ic manner than his predecessor, he yet criticised in a quite similar manner from that point of view the effort of the geometrical method to know reality by employing only logical forms. He rejected the ontological proof for the existence of God, since out of conceptions alone existence can never be inferred ; existence (as Kant expressed it) cannot be dug out of ideas. In the same line, also, was the exact distinguishing between the real relation of causes and effects and the logical relation of ground and consequent, which Crusius urged in his treatment of the principle of ground or reason. For his own part he used this difference between real and ideal grounds
to oppose the Leibnizo-Wolffian determinism, and especially to set up the Scotist conception of the unrestricted free will of the Creator, in opposition to the Thomist conception of the relation between the divine will and the divine intellect, which the rational ists maintained. The turning away from natural religion, which lay in all these inferences, made the stricter Protestant orthodoxy favourably disposed toward the doctrine of Crusius.
The investigation as to the fundamental difference in method between philosophy and mathematics, that cut deepest and was most important in results, was that undertaken by Kant, whose writings very early refer to Crusius. But in his prize treatise On the Clearness of the Principles of Natural Theology and Morals he brings a decisive statement. The two sciences are related as opj>o- site in every respect Philosophy is an analytic science of concep tions, mathematics a synthetic science of magnitudes: the former receives its conceptions, the latter constructs its magnitudes ; the former seeks definitions, the latter sets out from definitions; the former needs experience, the latter does not ; the former rests upon the activity of the understanding, the latter upon that of the sensibil ity. Philosophy, therefore, in order to know the real, must proceed irtetically : it must not try to imitate the constructive method of mathematics.
With this fundamental insight into the sensuous character of the cognitive foundations of mathematics, Kant exploded the system of the geometrical method. For, according to his view, sensibility and understanding can no longer be distinguished as lower and higher grades of clearness and distinctness in knowledge. Mathematics proves that sensuous knowledge can be very clear and distinct, and many a system of metaphysics proves that intellectual knowledge may be very obscure and confused. The old distinction must there fore be exchanged for another, and Kant attempts a substitute by
486 The Enlightenment : Theoretical Questions. [Pakt V:
defining sensibility as the faculty of receptivity, understanding as that of spontaneity. He does this in his Inaugural Dissertation, and upon this builds a new system of epistemology,' leaning upon the psychological principle of virtual innateness (cf. § 33, 12).
The main outlines of the system are the following : the Forms of the sensibility are space and time ; those of the understanding are the most general conceptions. Out of reflection upon the one class arises mathematics ; upon the other class, metaphysics; — both a priori sciences of unconditional certainty. But Forms of (receptive) sen sibility give only the necessary knowledge of the appearance of things in the human mind (mundus sensibilis phaznomenon) ; the Forms of the understanding, on the contrary, give adequate knowl edge of the true essential nature of things (mundus intelUgibilis nou-
That these Forms of the understanding are able to do this is due to the fact, that the understanding, as well as things them
selves, has its origin in the divine mind; that we, therefore, means of see things to certain extent " in God. "
35.
lb. IV. 2.
»Ib. II. 23,20; IV. 10. 9.
»1
8, 7
a
is,
Chap. 1, § 34. ] Knowledge of the Order World : Berkeley . 469
roent of the cogito ergo sum. This principle he carries over entirely from the metaphysical realm into that of empirical psychology. . . Self-certainty is for him thafr^jftne " internal sense " ; intuition in this case refers only to our states and activities, not to our essence ; it shows us, indeed, immediately and without doubt, that we are, but not what we are. The question a^ to the substance of the soul (and accordingly the question als»> As torts relation to the body) is as incapable of an answer as the question as to the " what" of any substance whatever.
Nevertheless, Locke holds it to be possible to gain a demonstrative certainty of the existence of Ood. For this purpose he adopts the first of the Cartesian proofs (cf. § 30, 5) in a somewhat modified form, and adds the ordinary cosmological argument An infinite, eternal, and perfect being must be thought, an ultimate cause of finite substances of which man intuitively knows himself to be one.
So manifold and full of contradictions are the motifs which cross in Locke's doctrine of knowledge. The exposition, apparently so easy and transparent, to which he diluted Cartesianism, glides over and away from the eddies which come up out of the dark depths of its historical presuppositions. But as the ambiguous, indeterminate nature of his psychology unfolded itself in the antithesis in the fol lowing developments, so, too, this episteinological metaphysics offered points of departure for the most varied transformations.
2. The very first of these shows an audacious energy of one-sided- ness in contrast with the indecisiveness of Locke. Berkeley brought the ascendeucy of inner experience to complete dominance by putting an end to the wavering position which Locke had taken upon the question as to the knowledge of bodies. This he did with the aid of his extreme Nominalism and with a return to the doctrines of Hobbes. He demolished the conception of corporeal substance. Ac cording to the distinction of primary and secondary qualities, it was held that a part of that complex of ideas which perception presents us as a body should be separated out, and another part retained as alone real; but this distinction, as Hobbes had already taught (cf. f 31, 2), is in the nature of the case erroneous. The "mathe matical " qualities of ladies are as truly ideas within us as the sense qualities, and Berkeley had demonstrated exactly this point with analogous arguments in his Theory of Vi»ion. He attacks the warrant of the distinction of Descartes (and of Democritus). But while, according to this view, all qualities of bodies without excep
tion are ideas in us, Locke has retained as their real supporter a superfluous unknowable "substance " ; in a similar way others speak of matter as the substrate of sensible qualities.
470 The Enlightenment : Theoretical Questions. [Part V.
But in all these cases, says Berkeley, it is demanded of us to regard an abstraction as the only actual reality. Abstract ideas, however, do not exist, — they do not exist even in the mind, to say nothing of existing in natura rerum. Locke was then quite right in saying that no one could know this "substance ": no one can even think it; it is a fiction of the schools. For the naive consciousness, for "common sense," whose cause Berkeley professes to maintain against the artificial subtlety of philosophers, bodies are just exactly what is perceived, no more and no less ; it is only the philosophers who 3eek for something else behind what is perceived, — something mysterious, abstract, of which they themselves cannot say what it is. For the unperverted mind, body is what one sees, touches, tastes, smells, and hears : its esse is percipi.
Body is then nothing but a complex of ideas. If we abstract from a cherry all the qualities which can be perceived through any of the senses, what is left ? Nothing. The idealism which sees in a body nothing farther than a bundle of ideas is the view of the common man ; it should be that of philosophers also. Bodies possess no other reality than that of being perceived. It is false to suppose that there is in addition to this a substance inherent within them, which "appears" in their qualities. They are nothing but the sum of these qualities.
In reply to the question that lies close at hand, in what the differ ence consists between the " real " or actual body and that which is only imagined or dreamed of, if all bodies are only perceived, Berkeley answers with a spiritualistic metaphysics. The ideas which constitute the existence of the outer world are activities of spirits. Of the two Cartesian worlds only one has substantial existence ; only the res cogitantes are real substances, the res extensa are their ideas. But to finite spirits the ideas are given, and the origin of all ideas is to be sought only in the infinite Spirit, in God. The reality of bodies consists, therefore, in this, that their ideas are
communicated by God to finite spirits, and the order of succession in which God habitually does this we call laws of Nature. Hence Bishop Berkeley finds no metaphysical difficulty in supposing that God under certain circumstances departs from the usual order for some especial end, and in this case man speaks of miracles. Ou the other hand, a body is unreal which is presented only in the indi vidual mind according to the mechanism of memory or imagination, and without being at the same time communicated to the mind by God. And finally, since the actual corporeal world is thus changed into a system of ideas willed by God, the purposiveness which its arrangement and the order of its changes exhibit gives rise to no further oroblem.
Chap. 1, § 34. ] Knowledge of the Outer World : Collier. 471
The parallelism between this inference from Locke and that which Malebranche had drawn from Descartes is unmistakable ; and Malebranche and Berkeley are also at one in holding that God alone is the active force in the world, and that no individual thing is efficiently operative (cf. § 31, 8). It is extremely interesting to see how the extreme Realism of the Frenchman and the extreme Nominalism of the Englishman amount to the same thing. The grounds on which the views are based could not be more different : the result is the same. For what still separated the two could be easily removed out of the way. This was proved by a contemporary and countryman of Berkeley's, Arthur Collier (1680-1732) in his interesting treatise Clavis Universalis. 1 Malebranche,1 indeed, as a Cartesian, had not directly demurred to the reality of the corporeal world, but had held that we could understand the knowledge of this world by man, only on the hypothesis that the ideas of bodies in God are the common original, in accordance with which God pro duces, on the one hand, the actual bodies, and, on the other, the
ideas of these bodies in finite minds. Collier showed now that in this theory the reality of the corporeal world played a completely superfluous rSle : since no actual relation between the corporeal world and human ideas is assumed, the value of human ideas for knowledge remains quite the same if we posit only an ideal cor poreal world in God, and regard this as the real object of human knowledge.
The idealism, which proceeded in this way from the cogito ergo turn along several paths, was attended by still another paradox as a by-product, which is occasionally mentioned in the literature of the eighteenth century without any definite name or form. Each individual mind has certain, intuitive knowledge only of itself and of its states, nor does it know anything of other minds
through ideas, which refer primarily to bodies and by an argument from analogy are interpreted to indicate minds. If, however, the whole corporeal world is only an idea in the mind, every individual is ultimately certain only of his own existence ; the reality of all else, all other minds not excluded, is problematical and cannot be demonstrated. This doctrine was at that time designated as Egoism, now it is usually called Solipsism. It is a metaphysical
1 The alternative title of the book reads, A Xev> Inquiry after Trvth. being m Demonstration of the Son-Existence or Impossibility of an External World
It wwi edited together with Berkeley's treat in* in the (iennan •• Collection of the Principal Writings which deny the Reality of their oxen Body ( . '. ') and of the tehole Corporeal World," by Kechenbach (Koitock. 1766).
* Wh<>«e doctrine had become known in England by the agency especially of John Sorris (Essai (Tun Theorie du Monde Idial, Lond. 1704).
(Lond. 1123).
except
472 Tlit EnliyhteniHtnt : Theoretical Questions. [Part V
sport which must be left to the taste of the individual; for the solipsist refutes himself by beginning to prove his doctrine to others.
Thus, following in the train of the Meditations, in which Descartes recognised self-consciousness as the rescuing rock in the sea of doubt, the result was finally reached which Kant later characterised as a scandal to philosophy ; namely, that a proof was demanded for the reality of the outer world, and none adequate could be found. The French materialists declared that Berkeley's doctrine was an insane delusion, but was irrefutable.
3. The transformation of Locke's doctrine by Berkeley leads farther in a direct line to Hume's theory of knowledge. To the nominalistic denial of abstract ideas the penetrative and profound Scot attached his distinction of all intellectual functions into im pressions, and ideas which are copies of impressions ; and coincident with his distinction is that of intuitive and demonstrative knowl edge. Each kind of knowledge has its own kind of certainty. Intuitive knowledge consists simply in the affirmation of actually present impressions. What impressions I have, I can declare with absolute certainty. I can make no mistake in this, in so far as I keep within the bounds of simply stating that I have a perception possessing this or that simple or complex content, without adding any conceptions which would put any interpretation upon this content.
As among the most important of these impressions which have immediate intuitive certainty Hume reckons the relations in space and time of the contents of sensation, — the fixing of the co-exist ence or succession of elementary impressions. The spatial order in which the contents of perception present themselves is undoubtedly given immediately with the contents themselves, and we likewise possess a sure impression as to whether the different contents are perceived at the same time or in succession. Contiguity in space and time is therefore intuitively given together with the impres sions, and of these facts the human mind possesses a knowledge which is perfectly certain and in nowise to be questioned. Only,
in characterising Hume's doctrine, it must not be forgotten that this absolutely certain matter-of-fact quality, which belongs to impressions, is solely that of their presence as mental states. In this meaning and restriction intuitive knowledge embraces not only the facts of inner experience, but also those of outer experience, but at the price of recognising that the latter are properly only species of the former, — a knowledge, that of mental states.
Contiguity in space and time however, but the most elementary
is,
is,
Chap. J, $ 34. ] Knowledge of the Outer World: Hume. 478
form of association between perceptions ; besides this Hume reckons two other laws, those of resemblance (or contrast, respectively) and causality. As regards the former of these two forms of relation, we hare a clear and distinct impression of the likeness or unlike- ness of sensations, and of the different degrees of these ; it consists in the knowledge of the degree of resemblance in our own (sensi tive) action, and belongs therefore to the impressions of the inner sense, which Locke called reflection. On this is based, consequently, a demonstrative knowledge of complete certainty ; it concerns the forms of that comparison between magnitudes which we perform upon the given contents of our ideas, and is nothing but an analysis of the regularity with which this takes place. This demonstrative science is mathematics ; it develops the laws of equality and propor tion with reference to numbers and space, and Hume is inclined to concede a still higher epistemological value to arithmetic than to geometry. 1
4. But mathematics is also the sole demonstrative science; and is that just because it relates to nothing else than the possible rela tions between contents of ideas, and asserts nothing whatever as to any relation of these to a real world. In this way the terministic principle of Hobbes (cf. § 30, 3) is in complete control with Hume, but the latter proceeds still more consistently with his limitation of this theory to pure mathematics. Fo»Hume declares that no asser tion respecting the external world is capable of demonstration ; all our knowledge is limited to the ascertaining and verifying of
impressions, other.
and to the relations of these mental states to each
Hence it seems to Hume an unauthorised trenching of thought beyond its own territory, when the resemblance between ideas is interpreted as meaning metaphysical identity ; this is the case in
every employment of the conception of substance. Whence is this conception ? It is not perceived, it is not found as a content either in particular sensations or in their relations; substance is the unknown, indescribable support of the known contents of ideas. Whence this idea for which no impression is to be found in the whole circuit of sensations as its necessary original ? Its origin is to be sought in reflection. It is the copy of a frequei tly repeated
conjunction of ideas. By the repeated being together of impres sions, by the custom of the like ideational process there arises by virtue of the law of association of ideas the necessity of the idea of their co-existence, and the feeling of this associative necessity of the
' Treat. I. 2, 1 ; I. 3, 1.
474 The Enlightenment : Theoretical Questions. [Part V.
ideational process is thought as a real belonging together of the elements of association, i. e. as substance.
The thought-form of inherence is thus psychologically explained, and at the same time epistemologically rejected; nothing corre sponds to it further than the feeling of a likeness in the ideational conjunction ; and since we can never know anything of existence except by immediate sense-perception, the Reality of the idea of substance is incapable of proof. It is clear that Hume thus makes Berkeley's doctrine his own, so far as it concerns corporeal things.
But Berkeley had but half done his work upon the idea of substance. He found that bodies are only complexes of sensations ; that their being is identical with their being perceived ; that there is no sense or meaning in hypostatising their belonging together, as an unknown substance : but he let the psychical substances, spirits, the res cogi- tantes, stand ; he regarded them as the supports or agents in which all these ideational activities inhere. Hume's argument applies to this latter class also. What Berkeley showed of the cherry is true also of the " self. " Inner perception, also (such was the form which it had actually taken on already with Locke; cf. above, No. 1), shows only activities, states, qualities. Take these away, and noth ing remains of Descartes' res cogiians either : only the " custom " of constant conjunction of ideas in imagination is at the basis of the conception of a "mind"; the self is only a " bundle of perceptions. " '
The same consideration holds also, mxttatis mutandis, for causality, that form under which the necessary connection between contents of ideas is usually thought : but this is neither intuitively nor de monstratively certain. The relation of cause and effect is not per ceived ; all that we can perceive by the senses is the relation in time, according to which one regularly follows the other. If, now, thought interprets this sequence into a consequence, this post hoc into a propter hoc,1 this too has no basis in the content of the ideas causally related to each other. From a "cause" it is not possible to deduce logically its " effect " ; the idea of an effect does not con tain within it that of its cause. It is not possible to understand the causal relation analytically. ' Its explanation is, according to
1 Treat. I. , Part IV. The objectionable consequences ■which resulted from this for religious metaphysics perhaps occasioned Hume, when working over his Treatise into the Essays, to let drop this which cut most deeply of all his investigations.
2 In this respect Hume had a forerunner in his countryman Joseph Glanril (1636-1680), who combated the mechanical natural philosophy from the stand point of orthodox scepticism in his Scepsis Scientifica, 1665.
* The same thought lay already at the basis of the Occasionalistic meta physics (cf. § 31, 7); for the essential reason for its taking refuge in mediation by the will of God was the logical incomprehensibility of the causal relation.
Chap. 1, $ 34. ] Knowledge of the Outer World : Hume. 47?
Hume, to be gained by means of association of ideas. Through the repetition of the same succession of ideas, and the custom of finding them follow each other, an inner necessity or compulsion arises of imagining and expecting the second after the first ; and the feeling of this inner necessity with which one idea calls up another is inter preted as a real objective necessity, as if the object corresponding to the first idea forced that corresponding to the other to a real existence in natura rerum. The impression in this case [of which the idea of cause and effect is a copy] is the necessary relation between the ideational activities [activities of the "imagination"], and from this arises, in the idea of causality, the idea of a neces sary relation between the ideational contents [i. e. that A. causes 8 ; whereas the case really is that the idea of A causes the idea of B, i. e. recalls it by the law of association].
[In view of the extreme condensation of the above statement, a fuller outline of Hume's discussion of causality may be useful. As found in the Treatise it is briefly as follows: All knowledge as to matters of fact ("probability"), if it goes beyond the bare present sensation, depends on causation. Tins contains three essential elements, — contiguity, succession, and necessary connection. We can explain the first two (i. e. can find the impression from which they come), but no impression of sensation can be fountt for the third and most impor tant. To aid in the search for its origin we examine the principle both in its general form and in its particular application, asking (1), why we say that whatever begins to exist must have a cause, and (2), why we conclude that a particular cause must necessarily have a particular effect.
(1) Kxamination of the first gives the negative result that the principle is not intuitively or demonstratively certain (the opposite is not inconceivable), hence it is not derived purely a priori, i. e. by analysing relations between ideas ; therefore it must be from experience. — (2) But hoic from experience? Taking for convenience the second question stated above, the particular instead of the general, it is evident (a) that the senses cannot tell that a particular effect will follow a given cause ; they are limited to the present. Nor (6) can such knowl edge as to future events be gained by reasoning on experience, as this would involve knowing that Instances of which we have had no experience must resemble those of which we had experience (would assume the uniformity of Nature), (e) Therefore the principle apparently must come from the only remaining faculty, imagination. This seems at first Impossible, in view of the strong belief which attaches to these ideas (e. g. that fire will burn), in contra
distinction from ordinary ideas of fancy. The question as thus shifted now becomes: (3) Hine explain the fact that )ce believe that a particular effect will follow a given cause ? The only difference between the ideas of the senses and memory (in which we believe) and those of fancy (in which we do not) is that of the feeling joined with them. The ideas of memory are more strong and
The same was also recognised by Kant In his "Attempt to introduce the Concep tion of Segatite Quantities into Philosophy " (cf. the general remark at the close) in a manner essentially in agreement with Hume. And finally. Thomas Urotrn ( On Cause and Effect), who also is not disinclined to Occasionalism (cf. op. eft. , pp. 106 ff. ), in a very interesting way deduces psychologically, and at the same time rejects epistemolngically (ib. 184 ff. ), the demand for an "explaining" or "understanding" of the actual succession of facts in time. Perception shows causes and effects roughly. The explanation of the process consists, then, in it* analysis into particular, simple and elementary causal relations. By this means the illusion arise* as if these latter must be yet again made analytically com- piwhmaibie.
476 The Enlightenment : Theoretical Questions. [Pakt V
lively. Hence the problem is, What makes the idea (e. g. that fire will burn } so " lively " that I believe in it ?
and the solution is, that as I find this belief arising not from a single instance, but only from the constant conjunction of the two impressions, the liveliness must be due to custom, i. e. to the habitual association of the ideas. " All probable reasoning is nothing but a species of sensation. "
This same doctrine explains the origin of the idea of necessary connection. For this does not arise from one instance, but from several. Bepetition dis covers nothing new, nor does it produce anything new in the objects, but it does produce something in the mind, viz. a determination to pass from one object to its usual attendant. 'I lie idea of necessity must arise from some impression. There is no external impression that can give rise to hence must be an im pression of reflection, and the only one available that propensity which custom produces to pass from an object to the idea of its usual attendant. Xecessity something that exists in the mind, not in objects. This confirmed by compar ative psychology (animals infer from experience through custom), by the theory of probabilities, and (in the Inquiry) by the freedom of the will, since belief may be reached in all these without necessarily holding to any objective neces sary connection. — Tr. ]
In this way, Hume's theory of knowledge disintegrates the two fundamental conceptions about which the metaphysical movement of the seventeenth century had revolved. Substance and causality are relations between ideas, and cannot be proved or substantiated either by experience or by logical thought: they rest upon the fictitious substitution of impressions derived from reflection, for those of sensation. But with this, the ground completely taken from under the feet of the ordinary metaphysics, and in its place appears only epistemology. The metaphysics of things gives place to metaphysics of knowledge.
Hume's contemporaries characterised this result of his investi gations — especially out of regard for its consequences with respect
to religious metaphysics (cf. 35, — as Scepticism yet essentially different from those doctrines to which this name his torically belongs. The settling of facts by sense-experience is, for Hume, intuitive certainty mathematical relations pass for demon strative certainty but, as for all alleged assertions by means of conceptions ["by abstract reasoning"] with reference to a reality other than that belonging to ideas concerning matter of fact and
Hume cries, "Into the fire with it! " There no knowledge of what things are and how they work we can say only what we perceive by sensation, what arrangement in space and time and what relations of resemblance we experience between them. This doctrine absolutely consistent and honest empiricism: demands that the only source of knowledge perception, nothing further shall be mingled with this than what actually contains. With this, all theory, all examination of cause, all doctrine of the " true Being" behind "phenomena" excluded. 1 If we characterise
existence"],
Berkeley is, therefore, correctly understood only from the point of view of
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Chap. 1, § 34. ] Knowledge of the Outer World : Hume. 477
this standpoint as Positivism, in accordance with the terminology of our century, we may say that its systematic basis was established by Hume.
But England's deepest thinker gave to this radical theory of knowledge a characteristic supplement. The associations of ideas which lie at the basis of the conceptions of substance and causality are, indeed, attended by neither intuitive nor demonstrative certainty; instead of this, however, they are accompanied by a conviction which has its roots in feeling, a natural belief, which, unper verted by any theoretical reflections, asserts itself victoriously in man's practical procedures, and is completely adequate for the attainable ends of life and for the knowledge relating to these. On this rests the experience of daily life. To question this never came into Hume's mind : he only wishes to prevent this from playing the role of an experimental science, for which it is inadequate. With the entire earnestness of philosophical depth he unites an open vision for the needs of practical life.
7. For the reception of this positivism the intellectual temper was less favourable in England than in France. Here the renuncia tion of any attempt at a metaphysics of things lay already prepared in the fundamental sceptical tendency which had made its appear ance so repeatedly from the Cartesian philosophy ; and the preva lence of this temper had been especially furthered by Bayle, whose criticism was, indeed, in principle directed chiefly against the rational grounding of religious truths ; but at the same time applied to all knowledge reaching beyond the sensuous, and therefore to all meta physics. Besides this, there was in the French literature a freer tendency that belongs to men of the world, which had likewise been furthered by Bayle, and at the same time by the influence of Eng lishmen, — a tendency which would strip off the fetters of the system of the schools, and demanded the immediate reality of life instead of abstract conceptions. Thus Bacon's doctrine, with its limitation of science to physical and anthropological experience, became more rffirarious in France than in his own home. The " point de systeme " meets us here at"every step; no one any longer wishes to know
anything of the causes premieres," and this Baconian platform with all its encyclopaedic and programmatic extension was laid down by rTAlembert as the philosophical basis of the Encyclopaedia. *
Hume : his idealism to half positivism. He lays especial weight upon the point that behind the ideas of bodies we are not still to seek for something abstract, •omethlng existent in itself. If this principle be extended to minds, we have
Hume's doctrine ; for with the fall of Berkeley's spiritualistic metaphysics, the order of phenomena willed by (iod. to which he had reduced causality, falls also.
1 In the Ditcours Prtlimiiiairr.
478 The Enlightenment : Theoretical Questions. [Part V.
In Germany the Wolffian system was opposed with the "point de systeme " by men like Crousaz and Maupertuis on grounds of taste, and, in fact, the pedantry of this text-book philosophy offered many points of attack. In contrast with this the German Popular Philos ophy prided itself upon its absence of system ; as developed by Mendelssohn it would refrain from all subtleties as to that which cannot be experienced, and employ itself the more with that which is useful for men. And, lastly, we find a fine example of harmony with this temper in Kant's Dreams of a Ghost-Seer, where he lashes the architects of various artificial worlds of thought with sharp irony, and pours out copious scorn upon metaphysical endeavour with a gallows-humour which touches his own inclination in a most sensitive point. Among the German poets Wieland is in this same spirit the witty anti-metaphysician.
8. A very peculiar turn was taken by positivism, finally, in the later doctrine of Condillac. In him converge the lines of the French and the English Enlightenment, and he finds a positivistic synthesis of sensualism and rationalism, which may be regarded as the most perfect expression of modern terminism. His Logic l and his post humous Langue des Calculs developed this doctrine. It is built up essentially upon a theory of " signs " (signes). 2 Human ideas are all of them sensations, or transformations of such, and for these no especial powers of the soul are needed. 3 All knowledge consists in the consciousness of the relations of ideas, and the fundamental relation is that of equality. The business of thinking is only to bring out the relations of equality between ideas. 4 This is done by analysing the complexes of ideas into their constituent elements and then putting them together again: dicomposition des pMno- menes and composition des idles. The isolation of the constituent elements which is requisite for this can, however, be effected only with the aid of signs or language. All language is a method for the analysis of phenomena, and every such method is a "language. " The different kinds of signs give different "dialects" of the human language: as such Condillac distinguishes five, — the fingers (ges tures), sound-language, numbers, letters, and the signs of the infini tesimal calculus. Logic, as the universal grammar of all these
* This Condillac maintains against Locke, and indeed already in his TraiU des Sensations, and his school do the same against the Scots.
4 In these determinations lie suggestions from Hobbes as well as from Hume.
1 A text-book for " Polish professors. "
J After the Langue des Calculs became known, the Institute of Paris and the Berlin Academy gave out, almost at the same time, the theory of signs as the subject for. their prizes. At both places a great number of elaborations were presented, mostly of very inferior value.
Chap. 1, § 34. ] Knowledge of the Outer World : Condtllae. 479
languages, determines, therefore, mathematics also, and indeed the higher as well as the elementary, as special cases.
All science thus contains only transformations. The thing to be done is always to make out that the unknown, which one is seeking, is really something already known; that to find the equation which shall put the unknown x equal to composition of ideas
just for this end that the structures of perception must be
It evident that this but a new generalising mode of expression for Galileo's doctrine of the method of resolution and composition; but rises here upon purely sensualistic basis denies the constructive element which Hobbes
had so sharply emphasised and makes of thinking reckoning with only given quantities. In doing this rejects all thought of relation of these data to metaphysical reality, and sees in scientific knowledge only a structure built up of equations between contents of ideas in accordance with the principle mime est mtme. The human world of ideas completely isolated within itself, and truth cunsists only in the equations that can be expressed within this world by " signs. "
9. Indifferent as this Ideology professed to be metaphysically, its sensualistic basis, nevertheless, involved a materialistic metaphysics. Even though nothing was to be said as to the reality corresponding to sensations, there still remained in the background the popular idea that sensations are produced by bodies. On this account the cautious restraint that belonged to these positivistic consequences of sensualism needed only to be neglected to convert the anthropo logical materialism, which had developed in the psychological theories, into metaphysical and dogmatic materialism. And so Lamettrie spoke out with coquettish recklessness what many others
did not dare to confess to themselves, to say nothing of confessing or defending openly.
But other lines of thought in natural science, independently of ideology, were also driving toward materialism. Lamettrie had very rightly seen that the principle of the mechanical explanation
of Nature would ultimately tolerate nothing in addition to matter moved by its own forces long before Laplace gave the well-known answer that he did not need the " hypothesis of the deity " French natural philosophy had attained this standpoint. That the world of gravitation lives in itself was Newton's opinion also; but he believed that the first impulse for its motions must be sought in an action of God. Kant went step farther when he cried in his Natural History of the Heavens, "Give me matter, and will build
yoa a world. " He pledged himself to explain the whole universe
previously decomposed.
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480 Tlie Enlightenment : Theoretical Questions. [Part \
of the fixed stars after the analogy of the planetary system,1 and traced the origination of the individual heavenly bodies out of a fiery-fluid primitive condition solely to the opposed working of tbi two fundamental forces of matter, attraction and repulsion. But Kant was convinced that the explanation which is sufficient for solar systems shatters when applied to the blade of grass and the caterpillar ; the organism seems to him to be a miracle ( Wunder) in the world of mechanics.
The French philosophy of Nature sought to overcome this obstacle also, and to put the problem of organisation out of the world. Among the countless atom-complexes, it taught, there are also those which
the capacity of preserving and propagating themselves. Buffon, who pronounced and carried through with full energy this frequently expressed thought, gave to such atom-complexes the name organic molecules, and by assuming this conception all organic life might be regarded in principle as an activity of such molecules, which develops according to mechanical laws, in contact with the external world. 8 This had been already done by Spinoza, of whose theory of Nature Buffon frequently reminds us ; the latter, also, speaks of God and " Nature " as synonyms. This naturalism found in mechanics, accordingly, the common principle for all corporeal occurrence. But if now ideology taught that ideas and their transformations should be regarded as functions of organisms, if it no longer was regarded as impossible, but more and more seemed probable, that the thing which thinks is the same that is extended and moves, if Hartley and Priestley in England and Lamettrie in France showed that a change in consciousness is a function of the nervous system, — it was but a step from this to teach that ideas with all their transformations form only a special case of the mechanical activity of matter, only a particular kind of its forms of motion. While Voltaire had expressed the opinion that motion and sensation
might perhaps be attributes of the same unknown substance, this hylozoism changed suddenly into decided materialism as soon as the dependence of the psychical upon the physical was given the new interpretation of a likeness in kind between the two, and it is often only by soft and fine shades of expression that the one is
>The suggestion for this brilliant astro-physical hypothesis, to which Lam bert also came very near in his Kosmologischen Briefen, and which was devel oped later in a similar manner by Laplace, was due perhaps to a remark by
Buffon. Cf. O. Liebmann, Zur Analysis der Wirklichleeit, 2d ed. , p. 376.
2 This principle of Buffon was further developed later by Lamarck (Philoso-
phie Zoologique, Paris, 1809), who attempted to explain the transformation of organisms from the lower to the higher forms by a mechanical influence of the outer world, by adaptation to the environment-
possess
Chap. 1, { 34. ] Knowledge of the Outer World : Materialism. 481
converted into the other. This transition is presented in the writings of Robinet. He gives a metaphysical flight to the philos ophy of Nature. Finding support in the development system of the Leibnizian Monadology, he regards the graded scale of things as an infinite multiplicity of forms of existence, in which the two factors of corporeality and psychical function are mixed in all the different relations possible, so that the more the nature of a particular thing unfolds in the one direction, the less is its activity in the other. This holds true, also, according to Robinet, in the case of the vital movements of individual creatures ; the force which they use men tally is lost physically, and conversely. Regarded as a whole, however, the psychical life appears as a special form which the fundamental material activity of things is able to assume, to be later translated back again into its original form. Robinet thus regards ideas and activities of the will as mechanical transformations of the nervous activity which can be changed back again into that. Noth ing takes place psychically which was not predisposed in the physi cal form ; and the body, accordingly, receives in psychical impulses only the reaction of its own motion.
In the Systeme de la Nature materialism appears at last undis guised as a purely dogmatic metaphysics. It introduces itself with the Epicurean motive of wishing to free man from fear of the super- sensuous. It shall be shown that the supersensuous is only the invisible form of activity of the sensuous. No one has ever been able to think out anything of a supersensuous character that was not a faded after-image of the material. He who talks of idea and will, of soul and God, thinks of nervous activity, of his body and the world over again in an abstract form. For the rest, this " Bible of Materialism" presents no new doctrines or arguments in its pain fully instructive and systematically tedious exposition : yet a certain weight in its conception taken as a whole, a greatness of stroke in drawing the lines of its Weltanschauung, a harsh earnestness of pre sentation, is not to be mistaken. This is no longer a piquant play
of thoughts, but a heavy armed attack upon all belief in the imma terial world.
10. In spite of psycho-genetic opposition, the problem of knowl edge as conceived by the supporters of " innate ideas " was not all too unlike the view which obtained with the sensualists. The dual- istic presupposition assumed by both classes made it difficult for the latter to understand the conformity which the ideas called out in the mind by bodies bear to the bodies themselves. But it seemed almost more difficult still to understand that the mind should cog nise a world independent of by means of the development of the
it,
482 The Enlightenment : Theoretical Questions. [Part V.
thought-forms which are grounded in its own nature. And yet exactly this is an assumption so deeply rooted in human thought, that it passes for the most part as self-evident and a matter of course, not only for the naive consciousness, but also for philo sophical reflection. It was the mission of the Terminism, whose after-workings were active in modern philosophy, to shake this fun damental dogmatic conviction, and push forward for consideration the question as to the ground of that conformity between necessity of thought, on the one hand, and reality on the other. Even Des cartes had found it necessary to support the knowing power of the lumen naturale by the veroxitas dei, and thereby had shown the only way which the metaphysical solution of the problem could take.
To be sure, where that philosophical impulse was lacking which directs its 0aiyia£«v — its wonder — upon just that which is appar ently self-evident and a matter of course, the difficulty just men tioned weighed less heavily. This was the case with Wolff, in spite of all his power of logical clearness and systematic care, and with the Scots, in spite of all their fineness of psychological analysis. The former proceeds to deduce, more yeometrico, an extensive ontol ogy, and a metaphysics with its parts relating to God, to the world, and to the soul, all from the most general formal laws of logic, — from the principle of contradiction and that of sufficient reason (and this second principle is even to be reduced to the first). Wolff, indeed, stands so completely within the bounds of this logical schematism that the question never seems to occur to him at all, whether his whole undertaking — namely, that of spinning "a sci ence of all that is possible, in so far as it is possible " out of logical propositions — is authorised in the nature of the case. This problem was concealed for him the more as he confirmed every rational science by an empirical science [e. g. Rational by Empirical Psychol ogy, etc. ], — an agreement, indeed, which was possible only because his a priori construction of metaphysical disciplines borrowed from
experience step by step, though the loan was unnoticed. Neverthe less, this system, which was blessed with so many disciples, had the great didactic value of setting up and naturalising strictness in thought, clearness of conceptions, and thoroughness in proof, as the supreme rules for science, and the pedantry which unavoidably stole in with these found a sufficient counterpoise in other intellectual forces.
The Scottish philosophy contented itself with seeking out the principles of sound common sense. Every sensation is the sign — Reid too, thinks as terministically as this — of the presence of an object; thinking guarantees the reality of the subject; whatever
Chap. 1, § 34. ] Knowledge of the Outer World : Leibniz. 483
actually comes into being must have a cause, etc. Such principles are absolutely certain; to deny them or even to doubt them is absurd. This is especially true, also, of the principle that what the understanding recognises clearly and distinctly is necessarily so.
In this is formulated the general principle of a philosophical atti tude which is called dogmatism (after Kant), unconditional confi dence in the agreement of thought with reality. The above examples of the particular principles show how eclectically this common sense sought to gather its fundamental truths from the different systems of philosophy. In this respect the " gesunde Menschen verstand "
[sound common sense] of the German popular philosophers was entirely in accord with it. Mendelssohn, like Reid, was of the opinion that all extremes in philosophy were errors, and that the truth lay in the mean position : every radical view has a germ of truth which has been forced artificially to a one-sided and diseased development A sound, healthy thinking (Nicolai, especially, lays weight on this predicate) does justice to all the different motives and so finds as its philosophy — the opinion of the average man.
11. In the mind of Leibniz the problem was solved by the hypothesis of the pre-established harmony. The monad knows the world because it is the world: the content which it represents is from the beginning the universe, and the law of the monad's activity is the law of the world. On account of its " having no windows " it has no experience at all in the proper sense: nevertheless the possibility of knowing the world is so established in its very essence that all its states must be regarded as just such a knowledge. There is, accordingly, no difference between intellect and sensibility, either
as regards the objects to which they refer, or as regards the way in which consciousness relates itself to these objects : the only differ ence is that sensibility cognises the indistinct phenomenal form, while intellect cognises the true essence of things. From a scientific point of view, therefore, knowledge by the senses was treated partly as the imperfect, preliminary stage, partly as the indistinct anti-type for the intellect's insight : the " historical " sciences were regarded either as preparations for the philosophical, or as lower appendages.
From this relation a ]>eculiar consequence resulted. The sensuous niode of representation, too, has a certain peculiar perfection of its own, which differs from the clearness and distinctness of intellectual knowledge in apprehending the phenomenal form of its object with out any consciousness of grounds or reasons : and in this perfection, characteristic of sensuous knowledge, Leibniz , had set the feeling oj
> Cf. esp. Princ. dt la Sat. etdela Grace, 17.
484 The Enlightenment: Theoretical Quettiont. [Part V.
the beautiful. When, now, one of Wolff's disciples, Alexander Baum-
in whom the architectonic impulse toward systeinatisation was developed to a particularly high degree, wished to place by the side of logic as the science of the perfect use of the intellect, a corre sponding science of the perfection of sensation, an aesthetics, this dis cipline took on the form of a science of the beautiful. 1 Thus aesthetics,* as a branch of philosophical knowledge, grew up, not out of interest in its subject-matter, but with a decided depreciation of it ; and as a " step-sister " [lit. posthumous : nachgeborene Schwester'] of logic she was treated by the latter with very little understanding for her own peculiar nature, and with a cool intellectual pedantry. Moreover, this last-named rationalist, who followed Leibniz in regarding the actual world as the best, and therefore, as the most beautiful among all possible worlds, could set up no other principle for the theory of art than the sensualistic one of imitating Nature, and developed this principle essentially into a tedious poetics. But in spite of this, it remains Baumgarten's great service to have treated the beautiful again, and for the first time in modern philosophy, in a systematic way from the general conceptions of philosophy, and by so doing to have founded a discipline that was destined to play so important a part in the further development of philosophy, especially in that of Germany.
12. The Leibnizo-Wolffian conception of the relation between sense and understanding, and especially the geometrical viethod introduced for rational knowledge, encountered numerous opponents in the German philosophy of the eighteenth century, whose opposi tion proceeded not only from the incitements of English and French sensualism and empiricism, but from independent investigations as to the methodical and epistemological relation between mathematics and
philosophy.
In this latter line Rudiger, and, stimulated by him, Crusius, con
tended most successfully against the Wolffian doctrine. In oppos; tion to Wolff's definition of philosophy as the science of the possible, Rudiger asserted that its task is to know the actual. Mathematics, and, therefore, also a philosophy which imitates the methods of mathematics, have to do only with the possible, with the contradic- tionless agreement of ideas with one another ; a true philosophy needs the real relation of its conceptions to the actual, and such a
gotten,
1 Cf. H. Lotze, Gesch. der Aesthetik in Deutschland (Munich, 1868).
2 The name " aesthetics " was then adopted at a later time by Kant, after some resistance at first, for the designation of the philosophical doctrine of the beautiful and of art, and from him passed over to Schiller, and through the latter' s writings into general use.
Chat. 1, § 34. ] Knowledge of the Outer World: Kant. 485
relation is to be gained only by perception. Crusius made this point of view his own ; and although he thought in a less sensual ist ic manner than his predecessor, he yet criticised in a quite similar manner from that point of view the effort of the geometrical method to know reality by employing only logical forms. He rejected the ontological proof for the existence of God, since out of conceptions alone existence can never be inferred ; existence (as Kant expressed it) cannot be dug out of ideas. In the same line, also, was the exact distinguishing between the real relation of causes and effects and the logical relation of ground and consequent, which Crusius urged in his treatment of the principle of ground or reason. For his own part he used this difference between real and ideal grounds
to oppose the Leibnizo-Wolffian determinism, and especially to set up the Scotist conception of the unrestricted free will of the Creator, in opposition to the Thomist conception of the relation between the divine will and the divine intellect, which the rational ists maintained. The turning away from natural religion, which lay in all these inferences, made the stricter Protestant orthodoxy favourably disposed toward the doctrine of Crusius.
The investigation as to the fundamental difference in method between philosophy and mathematics, that cut deepest and was most important in results, was that undertaken by Kant, whose writings very early refer to Crusius. But in his prize treatise On the Clearness of the Principles of Natural Theology and Morals he brings a decisive statement. The two sciences are related as opj>o- site in every respect Philosophy is an analytic science of concep tions, mathematics a synthetic science of magnitudes: the former receives its conceptions, the latter constructs its magnitudes ; the former seeks definitions, the latter sets out from definitions; the former needs experience, the latter does not ; the former rests upon the activity of the understanding, the latter upon that of the sensibil ity. Philosophy, therefore, in order to know the real, must proceed irtetically : it must not try to imitate the constructive method of mathematics.
With this fundamental insight into the sensuous character of the cognitive foundations of mathematics, Kant exploded the system of the geometrical method. For, according to his view, sensibility and understanding can no longer be distinguished as lower and higher grades of clearness and distinctness in knowledge. Mathematics proves that sensuous knowledge can be very clear and distinct, and many a system of metaphysics proves that intellectual knowledge may be very obscure and confused. The old distinction must there fore be exchanged for another, and Kant attempts a substitute by
486 The Enlightenment : Theoretical Questions. [Pakt V:
defining sensibility as the faculty of receptivity, understanding as that of spontaneity. He does this in his Inaugural Dissertation, and upon this builds a new system of epistemology,' leaning upon the psychological principle of virtual innateness (cf. § 33, 12).
The main outlines of the system are the following : the Forms of the sensibility are space and time ; those of the understanding are the most general conceptions. Out of reflection upon the one class arises mathematics ; upon the other class, metaphysics; — both a priori sciences of unconditional certainty. But Forms of (receptive) sen sibility give only the necessary knowledge of the appearance of things in the human mind (mundus sensibilis phaznomenon) ; the Forms of the understanding, on the contrary, give adequate knowl edge of the true essential nature of things (mundus intelUgibilis nou-
That these Forms of the understanding are able to do this is due to the fact, that the understanding, as well as things them
selves, has its origin in the divine mind; that we, therefore, means of see things to certain extent " in God. "
35.
