No More Learning

Mathematics holds an intermediate position, since in it,
one of these qualifications is removed, but the other still remains, for
the geometer's figures are boundaries and limits of sensible bodies, and
the arithmetician's numbers properties of collections of concrete
objects. It follows also that the initial axioms or postulates of
Mathematics form a less simple system than those of First Philosophy,
and those of Physics than those of Mathematics. Mathematics requires as
initial assumptions not only those which hold good for _all_ thought,
but certain other special axioms which are only valid and significant
for the realm of figure and number; Physics requires yet further axioms
which are only applicable to "what is in motion. " This is why, though
the three disciplines are treated as distinct, they are not strictly
co-ordinate, and "First Philosophy," though "first," is only _prima
inter pares_.

We thus get the following diagrammatic scheme of the classification of
sciences:--

Science
|
+-----------+------------+
| |
Theoretical Practical
|
+---+---------+-----------+
| | |
First Philosophy Mathe- Physics
or matics
Theology


Practical Philosophy is not subjected by Aristotle to any similar
subdivision. Later students were accustomed to recognise a threefold
division into Ethics (the theory of individual conduct), Economics (the
theory of the management of the household), Politics (the theory of the
management of the State). Aristotle himself does not make these
distinctions. His general name for the theory of conduct is Politics,
the doctrine of individual conduct being for him inseparable from that
of the right ordering of society. Though he composed a separate course
of lectures on individual conduct (the _Ethics_), he takes care to open
the course by stating that the science of which it treats is Politics,
and offers an apology for dealing with the education of individual
character apart from the more general doctrine of the organisation of
society. No special recognition is given in Aristotle's own
classification to the Philosophy of Art. Modern students of Aristotle
have tried to fill in the omission by adding artistic creation to
contemplation and practice as a third fundamental form of mental
activity, and thus making a threefold division of Philosophy into
Theoretical, Practical, and Productive. The object of this is to find a
place in the classification for Aristotle's famous _Poetics_ and his
work on Rhetoric, the art of effective speech and writing. But the
admission of the third division of Science has no warrant in the text of
Aristotle, nor are the _Rhetoric_ and _Poetics_, properly speaking, a
contribution to Philosophy. They are intended as collections of
practical rules for the composition of a pamphlet or a tragedy, not as a
critical examination of the canons of literary taste. This was
correctly seen by the dramatic theorists of the seventeenth century.
They exaggerated the value of Aristotle's directions and entirely
misunderstood the meaning of some of them, but they were right in their
view that the _Poetics_ was meant to be a collection of rules by obeying
which the craftsman might make sure of turning out a successful play.
So far as Aristotle has a Philosophy of Fine Art at all, it forms part
of his more general theory of education and must be looked for in the
general discussion of the aims of education contained in his _Politics_.

*The Methods of Science*. --No place has been assigned in the scheme to
what we call logic and Aristotle called _Analytics_, the theory of
scientific method, or of proof and the estimation of evidence. The
reason is that since the fundamental character of proof is the same in
all science, Aristotle looks upon logic as a study of the methods common
to all science. At a later date it became a hotly debated question
whether logic should be regarded in this way as a study of the methods
instrumental to proof in all sciences, or as itself a special
constituent division of philosophy. The Aristotelian view was concisely
indicated by the name which became attached to the collection of
Aristotle's logical works. They were called the _Organon_, that is, the
"instrument," or the body of rules of method employed by Science. The
thought implied is thus that logic furnishes the _tools_ with which
every science has to work in establishing its results. Our space will
only permit of a brief statement as to the points in which the
Aristotelian formal logic appears to be really original, and the main
peculiarities of Aristotle's theory of knowledge.

(a) *Formal Logic*. --In compass the Aristotelian logic corresponds
roughly with the contents of modern elementary treatises on the same
subject, with the omission of the sections which deal with the so-called
Conditional Syllogism. The inclusion of arguments of this type in
mediaeval and modern expositions of formal logic is principally due to
the Stoics, who preferred to throw their reasoning into these forms and
subjected them to minute scrutiny. In his treatment of the doctrine of
Terms, Aristotle avoids the mistake of treating the isolated name as
though it had significance apart from the enunciations in which it
occurs. He is quite clear on the all-important point that the unit of
thought is the proposition in which something is affirmed or denied, the
one thought-form which can be properly called "true" or "false. " Such
an assertion he analyses into two factors, that about which something is
affirmed or denied (the Subject), and that which is affirmed or denied
of it (the Predicate). Consequently his doctrine of the classification
of Terms is based on a classification of Predicates, or of Propositions
according to the special kind of connection between the Subject and
Predicate which they affirm or deny. Two such classifications, which
cannot be made to fit into one another, meet us in Aristotle's logical
writings, the scheme of the ten "Categories," and that which was
afterwards known in the Middle Ages as the list of "Predicaments" or
"Heads of Predicates," or again as the "Five Words. " The list of
"Categories" reveals itself as an attempt to answer the question in how
many different senses the words "is a" or "are" are employed when we
assert that "_x_ is _y_" or "_x_ is a _y_" or "_x_s are _y_s. " Such a
statement may tell us (1) what _x_ is, as if I say "_x_ is a lion"; the
predicate is then said to fall under the category of Substance; (2) what
_x_ is like, as when I say "_x_ is white, or _x_ is wise,"--the category
of Quality; (3) how much or how many _x_ is, as when I say "_x_ is tall"
or "_x_ is five feet long,"--the category of Quantity; (4) how _x_ is
related to something else, as when I say "_x_ is to the right of _y_,"
"_x_ is the father of _y_,"--the category of Relation. These are the
four chief "categories" discussed by Aristotle. The remainder are (5)
Place, (6) Time, (7) and (8) Condition or State, as when I say "_x_ is
sitting down" or "_x_ has his armour on,"--(the only distinction between
the two cases seems to be that (7) denotes a more permanent state of _x_
than (8)); (9) Action or Activity, as when I say "_x_ is cutting," or
generally "_x_ is doing something to _y_"; (10) Passivity, as when I say
"_x_ is being cut," or more generally, "so-and-so is being done to _x_. "
No attempt is made to show that this list of "figures of predication" is
complete, or to point out any principle which has been followed in its
construction. It also happens that much the same enumeration is
incidentally made in one or two passages of Plato. Hence it is not
unlikely that the list was taken over by Aristotle as one which would be
familiar to pupils who had read their Plato, and therefore convenient
for practical purposes. The fivefold classification does depend on a
principle pointed out by Aristotle which guarantees its completeness,
and is therefore likely to have been thought out by him for himself, and
to be the genuine Aristotelian scheme. Consider an ordinary universal
affirmative proposition of the form "all _x_s are _y_s. " Now if this
statement is true it may also be true that "all _y_s are _x_s," or it
may not. On the first supposition we have two possible cases, (1) the
predicate may state precisely what the subject defined _is_; then _y_ is
the Definition of _x_, as when I say that "men are mortal animals,
capable of discourse. " Here it is also true to say that "mortal animals
capable of discourse are men," and Aristotle regards the predicate
"mortal animal capable of discourse" as expressing the inmost nature of
man. (2) The predicate may not express the inmost nature of the
subject, and yet may belong only to the class denoted by the subject and
to every member of that class. The predicate is then called a Proprium
or property, an exclusive attribute of the class in question. Thus it
was held that "all men are capable of laughter" and "all beings capable
of laughter are men," but that the capacity for laughter is no part of
the inmost nature or "real essence" of humanity. It is therefore
reckoned as a Proprium.

Again in the case where it is true that "all _x_s are _y_s," but not
true that all "_y_s are _x_s," _y_ may be part of the definition of _x_
or it may not. If it is part of the definition of _x_ it will be either
(3) a genus or wider class of which _x_ forms a subdivision, as when I
say, "All men are animals," or (4) a difference, that is, one of the
distinctive marks by which the _x_s are distinguished from other
sub-classes or species of the same genus, as when I say, "All men are
capable of discourse. " Or finally (5) _y_ may be no part of the
definition of _x_, but a characteristic which belongs both to the _x_s
and some things other than _x_s. The predicate is then called an
Accident. We have now exhausted all the possible cases, and may say
that the predicate of a universal affirmative proposition is always
either a definition, a proprium, a genus, a difference, or an accident.
This classification reached the Middle Ages not in the precise form in
which it is given by Aristotle, but with modifications mainly due to the
Neo-Platonic philosopher Porphyry. In its modified form it is regarded
as a classification of terms generally. Definition disappears from the
list, as the definition is regarded as a complex made up of the genus,
or next highest class to which the class to be defined belongs, and the
differences which mark off this particular species or sub-class. The
species itself which figures as the subject-term in a definition is
added, and thus the "Five Words" of mediaeval logic are enumerated as
genus, species, difference, proprium, accident.

The one point of philosophical interest about this doctrine appears
alike in the scheme of the "Categories" in the presence of a category of
"substance," and in the list of "Predicaments" in the sharp distinction
drawn between "definition" and "proprium. " From a logical point of view
it does not appear why _any_ proprium, _any_ character belonging to all
the members of a class and to them alone, should not be taken as
defining the class. Why should it be assumed that there is only _one_
predicate, viz. _man_, which precisely answers the question, "What is
Socrates? " Why should it not be equally correct to answer, "a Greek,"
or "a philosopher"? The explanation is that Aristotle takes it for
granted that not all the distinctions we can make between "kinds" of
things are arbitrary and subjective. Nature herself has made certain
hard and fast divisions between kinds which it is the business of our
thought to recognise and follow. Thus according to Aristotle there is a
real gulf, a genuine difference in kind, between the horse and the ass,
and this is illustrated by the fact that the mule, the offspring of a
horse and an ass, is not capable of reproduction. It is thus a sort of
imperfect being, a kind of "monster" existing _contra naturam_. Such
differences as we find when we compare _e. g. _ Egyptians with Greeks do
not amount to a difference in "kind. " To say that Socrates is a man
tells me what Socrates is, because the statement places Socrates in the
real kind to which he actually belongs; to say that he is wise, or old,
or a philosopher merely tells me some of his attributes. It follows from
this belief in "real" or "natural" kinds that the problem of definition
acquires an enormous importance for science. We, who are accustomed to
regard the whole business of classification as a matter of making a
grouping of our materials such as is most pertinent to the special
question we have in hand, tend to look upon any predicate which belongs
universally and exclusively to the members of a group, as a sufficient
basis for a possible definition of the group. Hence we are prone to
take the "nominalist" view of definition, _i. e. _ to look upon a
definition as no more than a declaration of the sense which we intend
henceforward to put on a word or other symbol. And consequently we
readily admit that there may be as many definitions of a class as it has
different propria. But in a philosophy like that of Aristotle, in which
it is held that a true classification must not only be formally
satisfactory, but must also conform to the actual lines of cleavage
which Nature has established between kind and kind, the task of
classificatory science becomes much more difficult. Science is called
on to supply not merely a definition but _the_ definition of the classes
it considers, _the_ definition which faithfully reflects the "lines of
cleavage" in Nature. This is why the Aristotelian view is that a true
definition should always be _per genus et differentias_. It should
"place" a given class by mentioning the wider class next above it in the
objective hierarchy, and then enumerating the most deep-seated
distinctions by which Nature herself marks off this class from others
belonging to the same wider class. Modern evolutionary thought may
possibly bring us back to this Aristotelian standpoint. Modern
evolutionary science differs from Aristotelianism on one point of the
first importance. It regards the difference between kinds, not as a
primary fact of Nature, but as produced by a long process of
accumulation of slight differences. But a world in which the process
has progressed far enough will exhibit much the same character as the
Nature of Aristotle. As the intermediate links between "species" drop
out because they are less thoroughly adapted to maintain themselves than
the extremes between which they form links, the world produced
approximates more and more to a system of species between which there
are unbridgeable chasms; evolution tends more and more to the final
establishment of "real kinds," marked by the fact that there is no
permanent possibility of cross-breeding between them. This makes it
once more possible to distinguish between a "nominal" definition and a
"real" definition. From an evolutionary point of view, a "real"
definition would be one which specifies not merely enough characters to
mark off the group defined from others, but selects also for the purpose
those characters which indicate the line of historical development by
which the group has successively separated itself from other groups
descended from the same ancestors. We shall learn yet more of the
significance of this conception of a "real kind" as we go on to make
acquaintance with the outlines of First Philosophy. Over the rest of
the formal logic of Aristotle we must be content to pass more rapidly.
In connection with the doctrine of Propositions, Aristotle lays down the
familiar distinction between the four types of proposition according to
their quantity (as universal or particular) and quality (as affirmative
or negative), and treats of their contrary and contradictory opposition
in a way which still forms the basis of the handling of the subject in
elementary works on formal logic. He also considers at great length a
subject nowadays commonly excluded from the elementary books, the modal
distinction between the Problematic proposition (_x_ may be _y_), the
Assertory (_x_ is _y_), and the Necessary (_x_ must be _y_), and the way
in which all these forms may be contradicted. For him, modality is a
formal distinction like quantity or quality, because he believes that
contingency and necessity are not merely relative to the state of our
knowledge, but represent real and objective features of the order of
Nature.

In connection with the doctrine of Inference, it is worth while to give
his definition of Syllogism or Inference (literally "computation") in
his own words. "Syllogism is a discourse wherein certain things (viz.
the premisses) being admitted, something else, different from what has
been admitted, follows of necessity because the admissions are what they
are. " The last clause shows that Aristotle is aware that the
all-important thing in an inference is not that the conclusion should be
novel but that it should be proved. We may have known the conclusion as
a fact before; what the inference does for us is to connect it with the
rest of our knowledge, and thus to show _why_ it is true. He also
formulates the axiom upon which syllogistic inference rests, that "if A
is predicated universally of B and B of C, A is necessarily predicated
universally of C. " Stated in the language of class-inclusion, and
adapted to include the case where B is denied of C this becomes the
formula, "whatever is asserted universally, whether positively or
negatively, of a class B is asserted in like manner of any class C which
is wholly contained in B," the axiom _de omni et nullo_ of mediaeval
logic. The syllogism of the "first figure," to which this principle
immediately applies, is accordingly regarded by Aristotle as the natural
and perfect form of inference. Syllogisms of the second and third
figures can only be shown to fall under the dictum by a process of
"reduction" or transformation into corresponding arguments in the first
"figure," and are therefore called "imperfect" or "incomplete," because
they do not exhibit the conclusive force of the reasoning with equal
clearness, and also because no universal affirmative conclusion can be
proved in them, and the aim of science is always to establish such
affirmatives. The list of "moods" of the three figures, and the
doctrine of the methods by which each mood of the imperfect figures can
be replaced by an equivalent mood of the first is worked out
substantially as in our current text-books. The so-called "fourth"
figure is not recognised, its moods being regarded merely as unnatural
and distorted statements of those of the first figure.

*Induction*. --Of the use of "induction" in Aristotle's philosophy we
shall speak under the head of "Theory of Knowledge. " Formally it is
called "the way of proceeding from particular facts to universals," and
Aristotle insists that the conclusion is only proved if _all_ the
particulars have been examined. Thus he gives as an example the
following argument, "_x_, _y_, _z_ are long-lived species of animals;
_x_, _y_, _z_ are the only species which have no gall; _ergo_ all
animals which have no gall are long-lived. " This is the "induction by
simple enumeration" denounced by Francis Bacon on the ground that it may
always be discredited by the production of a single "contrary instance,"
_e. g. _ a single instance of an animal which has no gall and yet is not
long-lived. Aristotle is quite aware that his "induction" does not
establish its conclusion unless all the cases have been included in the
examination. In fact, as his own example shows, an induction which
gives certainty does not start with "particular facts" at all. It is a
method of arguing that what has been proved true of each sub-class of a
wider class will be true of the wider class as a whole. The premisses
are strictly universal throughout. In general, Aristotle does not
regard "induction" as _proof_ at all. Historically "induction" is held
by Aristotle to have been first made prominent in philosophy by
Socrates, who constantly employed the method in his attempts to
establish universal results in moral science. Thus he gives, as a
characteristic argument for the famous Socratic doctrine that knowledge
is the one thing needful, the "induction," "he who understands the
theory of navigation is the best navigator, he who understands the
theory of chariot-driving the best driver; from these examples we see
that universally he who understands the theory of a thing is the best
practitioner," where it is evident that _all_ the relevant cases have
_not_ been examined, and consequently that the reasoning does not amount
to proof. Mill's so-called reasoning from particulars to particulars
finds a place in Aristotle's theory under the name of "arguing from an
example. " He gives as an illustration, "A war between Athens and Thebes
will be a bad thing, for we see that the war between Thebes and Phocis
was so. " He is careful to point out that the whole force of the
argument depends on the _implied_ assumption of a universal proposition
which covers both cases, such as "wars between _neighbours_ are bad
things. " Hence he calls such appeals to example "rhetorical" reasoning,
because the politician is accustomed to leave his hearers to supply the
relevant universal consideration for themselves.

*Theory of Knowledge*. --Here, as everywhere in Aristotle's philosophy,
we are confronted by an initial and insuperable difficulty. Aristotle
is always anxious to insist on the difference between his own doctrines
and those of Plato, and his bias in this direction regularly leads him
to speak as though he held a thorough-going naturalistic and empirical
theory with no "transcendental moonshine" about it. Yet his final
conclusions on all points of importance are hardly distinguishable from
those of Plato except by the fact that, as they are so much at variance
with the naturalistic side of his philosophy, they have the appearance
of being sudden lapses into an alogical mysticism. We shall find the
presence of this "fault" more pronouncedly in his metaphysics,
psychology, and ethics than in his theory of knowledge, but it is not
absent from any part of his philosophy. He is everywhere a Platonist
_malgre lui_, and it is just the Platonic element in his thought to
which it owes its hold over men's minds.

Plato's doctrine on the subject may be stated with enough accuracy for
our purpose as follows. There is a radical distinction between
sense-perception and scientific knowledge. A scientific truth is exact
and definite, it is also true once and for all, and never becomes truer
or falser with the lapse of time. This is the character of the
propositions of the science which Plato regarded as the type of what
true science ought to be, pure mathematics. It is very different with
the judgments which we try to base on our sense-perceptions of the
visible and tangible world. The colours, tastes, shapes of sensible
things seem different to different percipients, and moreover they are
constantly changing in incalculable ways. We can never be certain that
two lines which seem to our senses to be equal are really so; it may be
that the inequality is merely too slight to be perceptible to our
senses. No figure which we can draw and see actually has the exact
properties ascribed by the mathematician to a circle or a square. Hence
Plato concludes that if the word science be taken in its fullest sense,
there can be no science about the world which our senses reveal. We can
have only an approximate knowledge, a knowledge which is after all, at
best, probable opinion. The objects of which the mathematician has
certain, exact, and final knowledge cannot be anything which the senses
reveal. They are objects of _thought_, and the function of visible
models and diagrams in mathematics is not to present _examples_ of them
to us, but only to show us imperfect _approximations_ to them and so to
"remind" the soul of objects and relations between them which she has
never cognised with the bodily senses. Thus mathematical straightness
is never actually beheld, but when we see lines of less and more
approximate straightness we are "put in mind" of that absolute
straightness to which sense-perception only approximates. So in the
moral sciences, the various "virtues" are not presented in their
perfection by the course of daily life. We do not meet with men who are
perfectly brave or just, but the experience that one man is braver or
juster than another "calls into our mind" the thought of the absolute
standard of courage or justice implied in the conviction that one man
comes nearer to it than another, and it is these absolute standards
which are the real objects of our attention when we try to define the
terms by which we describe the moral life. This is the
"epistemological" side of the famous doctrine of the "Ideas. " The main
points are two, (1) that strict science deals throughout with objects
and relations between objects which are of a purely intellectual or
conceptual order, no sense-data entering into their constitution; (2)
since the objects of science are of this character, it follows that the
"Idea" or "concept" or "universal" is not arrived at by any process of
"abstracting" from our experience of sensible things the features common
to them all. As the particular fact never actually exhibits the
"universal" except approximately, the "universal" cannot be simply
disentangled from particulars by abstraction. As Plato puts it, it is
"apart from" particulars, or, as we might reword his thought, the pure
concepts of science represent "upper limits" to which the comparative
series which we can form out of sensible data continually approximate
but do not reach them.

In his theory of knowledge Aristotle begins by brushing aside the
Platonic view. Science requires no such "Ideas," transcending
sense-experience, as Plato had spoken of; they are, in fact, no more
than "poetic metaphors. " What is required for science is not that there
should be a "one over and above the many" (that is, such pure concepts,
unrealised in the world of actual perception, as Plato had spoken of),
but only that it should be possible to predicate one term universally of
many others. This, by itself, means that the "universal" is looked on
as a mere residue of the characteristics found in each member of a
group, got by abstraction, _i. e. _ by leaving out of view the
characteristics which are peculiar to some of the group and retaining
only those which are common to all. If Aristotle had held consistently
to this point of view, his theory of knowledge would have been a purely
empirical one. He would have had to say that, since all the objects of
knowledge are particular facts given in sense-perception, the universal
laws of science are a mere convenient way of describing the observed
uniformities in the behaviour of sensible things. But, since it is
obvious that in pure mathematics we are not concerned with the actual
relations between sensible data or the actual ways in which they behave,
but with so-called "pure cases" or ideals to which the perceived world
only approximately conforms, he would also have had to say that the
propositions of mathematics are not strictly true. In modern times
consistent empiricists have said this, but it is not a position possible
to one who had passed twenty years in association with the
mathematicians of the Academy, and Aristotle's theory only begins in
naturalism to end in Platonism. We may condense its most striking
positions into the following statement. By science we mean _proved_
knowledge. And proved knowledge is always "mediated"; it is the
knowledge of _conclusions_ from premisses. A truth that is
scientifically known does not stand alone. The "proof" is simply the
pointing out of the connection between the truth we call the conclusion,
and other truths which we call the premisses of our demonstration.
Science points out the _reason why_ of things, and this is what is meant
by the Aristotelian principle that to have science is to know things
through their _causes_ or _reasons why_. In an ordered digest of
scientific truths, the proper arrangement is to begin with the simplest
and most widely extended principles and to reason down, through
successive inferences, to the most complex propositions, the _reason
why_ of which can only be exhibited by long chains of deductions. This
is the order of logical dependence, and is described by Aristotle as
reasoning _from_ what is "more knowable in its own nature,"[#] the
simple, to what is usually "more familiar to _us_," because less removed
from the infinite wealth of sense-perception, the complex. In
_discovery_ we have usually to reverse the process and argue from "the
familiar to us," highly complex facts, to "the more knowable in its own
nature," the simpler principles implied in the facts.


[#] This simple expression acquires a mysterious appearance in mediaeval
philosophy from the standing mistranslation _notiora naturae_, "better
known to nature. "


It follows that Aristotle, after all, admits the disparateness of
sense-perception and scientific knowledge. Sense-perception of itself
never gives us scientific truth, because it can only assure us that a
fact is so; it cannot _explain_ the fact by showing its connection with
the rest of the system of facts, "it does not give the _reason_ for the
fact. " Knowledge of perception is always "immediate," and for that very
reason is never scientific. If we stood on the moon and saw the earth,
interposing between us and the sun, we should still not have scientific
knowledge about the eclipse, because "we should still have to ask for
the _reason why_. " (In fact, we should not know the reason _why_
without a theory of light including the proposition that light-waves are
propagated in straight lines and several others. ) Similarly Aristotle
insists that Induction does not yield scientific truth. "He who makes
an induction points out something, but does not demonstrate anything. "

For instance, if we know that _each_ species of animal which is without
a gall is long-lived, we may make the induction that _all_ animals
without a gall are long-lived, but in doing so we have got no nearer to
seeing _why_ or _how_ the absence of a gall makes for longevity. The
question which we may raise in science may all be reduced to four heads,
(1) Does this thing exist? (2) Does this event occur? (3) If the thing
exists, precisely what is it? and (4) If the event occurs, _why_ does it
occur? and science has not completed its task unless it can advance from
the solution of the first two questions to that of the latter two.
Science is no mere catalogue of things and events, it consists of
inquiries into the "real essences" and characteristics of things and the
laws of connection between events.

Looking at scientific reasoning, then, from the point of view of its
formal character, we may say that all science consists in the search for
"middle terms" of syllogisms, by which to connect the truth which
appears as a conclusion with the less complex truths which appear as the
premisses from which it is drawn. When we ask, "does such a thing
exist? " or "does such an event happen? " we are asking, "is there a
middle term which can connect the thing or event in question with the
rest of known reality? " Since it is a rule of the syllogism that the
middle term must be taken universally, at least once in the premisses,
the search for middle terms may also be described as the search for
universals, and we may speak of science as knowledge of the universal
interconnections between facts and events.

A science, then, may be analysed into three constituents. These are: (1)
a determinate class of objects which form the subject-matter of its
inquiries. In an orderly exhibition of the contents of the science,
these appear, as in Euclid, as the initial data about which the science
reasons; (2) a number of principles, postulates, and axioms, from which
our demonstrations must start. Some of these will be principles
employed in all scientific reasoning. Others will be specific to the
subject-matter with which a particular science is concerned; (3) certain
characteristics of the objects under study which can be shown by means
of our axioms and postulates to follow from our initial definitions, the
_accidentia per se_ of the objects defined. It is these last which are
expressed by the conclusions of scientific demonstration. We are said
to know scientifically that B is true of A when we show that this
follows, in virtue of the principles of some science, from the initial
definition of A. Thus if we convinced ourselves that the sum of the
angles of a plane triangle is equal to two right angles by measurement,
we could not be said to have scientific knowledge of the proposition.
But if we show that the same proposition follows from the definition of
a plane triangle by repeated applications of admitted axioms or
postulates of geometry, our knowledge is genuinely scientific. We now
know that it is so, and we see _why_ it is so; we see the connection of
this truth with the simple initial truths of geometry.

This leads us to the consideration of the most characteristic point of
Aristotle's whole theory. Science is demonstrated knowledge, that is,
it is the knowledge that certain truths follow from still simpler
truths. Hence the simplest of all the truths of any science cannot
themselves be capable of being known by inference. You cannot infer
that the axioms of geometry are true because its conclusions are true,
since the truth of the conclusions is itself a consequence of the truth
of the axioms.
Nor yet must you ask for demonstration of the axioms as
consequences of still simpler premisses, because if all truths can be
proved, they ought to be proved, and you would therefore require an
infinity of successive demonstrations to prove anything whatever. But
under such conditions all knowledge of demonstrated truth would be
impossible. The first principles of any science must therefore be
indemonstrable. They must be known, as facts of sense-perception are
known, immediately and not mediately. How then do we come by our
knowledge of them? Aristotle's answer to this question appears at first
sight curiously contradictory. He seems to say that these simplest
truths are apprehended intuitively, or on inspection, as self-evident by
Intelligence or Mind. On the other hand, he also says that they are
known _to us_ as a result of induction from sense-experience. Thus he
_seems_ to be either a Platonist or an empiricist, according as you
choose to remember one set of his utterances or another, and this
apparent inconsistency has led to his authority being claimed in their
favour by thinkers of the most widely different types. But more careful
study will show that the seeming confusion is due to the fact that he
tries to combine in one statement his answers to two quite different
questions, (1) how we come to reflect on the axioms, (2) what evidence
there is for their truth. To the first question he replies, "by
induction from experience," and so far he might seem to be a precursor
of John Stuart Mill. Successive repetitions of the same
sense-perceptions give rise to a single experience, and it is by
reflection on experience that we become aware of the most ultimate
simple and universal principles. We might illustrate his point by
considering how the thought that two and two are four may be brought
before a child's mind. We might first take two apples, and two other
apples and set the child to count them. By repeating the process with
different apples we may teach the child to dissociate the result of the
counting from the particular apples employed, and to advance to the
thought, "any two apples and any two other apples make four apples. "
Then we might substitute pears or cherries for the apples, so as to
suggest the thought, "two fruits and two fruits make four fruits. " And
by similar methods we should in the end evoke the thought, "any two
objects whatever and any other two objects whatever make four objects. "
This exactly illustrates Aristotle's conception of the function of
induction, or comparison of instances, in fixing attention on a
universal principle of which one had not been conscious before the
comparison was made.

Now comes in the point where Aristotle differs wholly from all
empiricists, later and earlier. Mill regards the instances produced in
the induction as having a double function; they not merely fix the
attention on the principle, they also are the evidence of its truth.
This gives rise to the greatest difficulty in his whole logical theory.
Induction by imperfect enumeration is pronounced to be (as it clearly
is) fallacious, yet the principle of the uniformity of Nature which Mill
regards as the ultimate premiss of all science, is itself supposed to be
proved by this radically fallacious method. Aristotle avoids a similar
inconsistency by holding that the sole function of the induction is to
fix our attention on a principle which it does not prove. He holds that
ultimate principles neither permit of nor require proof. When the
induction has done its work in calling attention to the principle, you
have to see for yourself that the principle is true. You see that it is
true by immediate inspection just as in sense-perception you have to see
that the colour before your eyes is red or blue. This is why Aristotle
holds that the knowledge of the principles of science is not itself
science (demonstrated knowledge), but what he calls intelligence, and we
may call intellectual intuition. Thus his doctrine is sharply
distinguished not only from empiricism (the doctrine that universal
principles are proved by particular facts), but also from all theories
of the Hegelian type which regard the principles and the facts as
somehow reciprocally proving each other, and from the doctrine of some
eminent modern logicians who hold that "self-evidence" is not required
in the ultimate principles of science, as we are only concerned in logic
with the question what consequences follow from our initial assumptions,
and not with the truth or falsehood of the assumptions themselves.

The result is that Aristotle does little more than repeat the Platonic
view of the nature of science. Science consists of deductions from
universal principles which sensible experience "suggests," but into
which, as they are apprehended by a purely intellectual inspection, no
sense-data enter as constituents. The apparent rejection of
"transcendental moonshine" has, after all, led to nothing. The only
difference between Plato and his scholar lies in the clearness of
intellectual vision which Plato shows when he expressly maintains in
plain words that the universals of exact science are not "in" our
sense-perceptions and therefore to be extracted from them by a process
of abstraction, but are "apart from" or "over" them, and form an ideal
system of interconnected concepts which the experiences of sense merely
"imitate" or make approximation to.

One more point remains to be considered to complete our outline of the
Aristotelian theory of knowledge. The sciences have "principles" which
are discerned to be true by immediate inspection. But what if one man
professes to see the self-evident truth of such an alleged principle,
while another is doubtful of its truth, or even denies it? There can be
no question of silencing the objector by a demonstration, since no
genuine simple principle admits of demonstration. All that can be done,
_e. g. _ if a man doubts whether things equal to the same thing are equal
to one another, or whether the law of contradiction is true, is to
examine the consequences of a denial of the axiom and to show that they
include some which are false, or which your antagonist at least
considers false. In this way, by showing the falsity of consequences
which follow from the denial of a given "principle," you indirectly
establish its truth. Now reasoning of this kind differs from "science"
precisely in the point that you take as your major premiss, not what you
regard as true, but the opposite thesis of your antagonist, which you
regard as false. Your object is not to prove a true conclusion but to
show your opponent that _his_ premisses lead to false conclusions. This
is "dialectical" reasoning in Aristotle's sense of the word, _i. e. _
reasoning not from your own but from some one else's premisses. Hence
the chief philosophical importance which Aristotle ascribes to
"dialectic" is that it provides a method of defending the undemonstrable
axioms against objections. Dialectic of this kind became highly
important in the mediaeval Aristotelianism of the schoolmen, with whom it
became a regular method, as may be seen _e. g. _ in the _Summa_ of St.
Thomas, to begin their consideration of a doctrine by a preliminary
rehearsal of all the arguments they could find or devise against the
conclusion they meant to adopt. Thus the first division of any article
in the _Summa Theologiae_ of Thomas is regularly constituted by arguments
based on the premisses of actual or possible antagonists, and is
strictly dialectical. (To be quite accurate Aristotle should, of
course, have observed that this dialectical method of defending a
principle becomes useless in the case of a logical axiom which is
presupposed by all deduction. For this reason Aristotle falls into
fallacy when he tries to defend the law of contradiction by dialectic.
It is true that if the law be denied, then any and every predicate may
be indifferently ascribed to any subject. But until the law of
contradiction has been admitted, you have no right to regard it as
absurd to ascribe all predicates indiscriminately to all subjects.
Thus, it is only assumed laws which are _not_ ultimate laws of logic
that admit of dialectical justification. If a truth is so ultimate that
it has either to be recognised by direct inspection or not at all, there
can be no arguing at all with one who cannot or will not see it. )




*CHAPTER III*

*FIRST PHILOSOPHY*


First Philosophy is defined by Aristotle as a "science which considers
What Is simply in its character of Being, and the properties which it
has as such. " That there is, or ought to be, such a science is urged on
the ground that every "special" science deals only with some restricted
department of what is, and thus considers its subject-matter not
universally in its character of being, or being real, but as determined
by some more special condition. Thus, First Philosophy, the science
which attempts to discover the most ultimate reasons of, or grounds for,
the character of things in general cannot be identified with any of the
"departmental" sciences. The same consideration explains why it is
"First Philosophy" which has to disentangle the "principles" of the
various sciences, and defend them by dialectic against those who impugn
them. It is no part of the duty of a geometer or a physicist to deal
with objections to such universal principles of reasoning as the law of
contradiction. They may safely assume such principles; if they are
attacked, it is not by specifically geometrical or physical
considerations that they can be defended. Even the "principles of the
special sciences" have not to be examined and defended by the special
sciences. They are the starting-points of the sciences which employ
them; these sciences are therefore justified in requiring that they
shall be admitted as a condition of geometrical, or physical, or
biological demonstrations. If they are called in question, the defence
of them is the business of logic.

First Philosophy, then, is the study of "What Is simply as such," the
universal principles of structure without which there could be no
ordered system of knowable objects. But the word "is" has more than one
sense. There are as many modes of being as there are types of
predication. "Substances," men, horses, and the like, have their own
specific mode of being--they are things; qualities, such as green or
sweet, have a different mode of being--they are not things, but
"affections" or "attributes" of things. Actions, again, such as
building, killing, are neither things nor yet "affections" of things;
their mode of being is that they are processes which produce or destroy
things. First Philosophy is concerned with the general character of all
these modes of being, but it is specially concerned with that mode of
being which belongs to _substances_. For this is the most primary of
all modes of being. We had to introduce a reference to it in our
attempt to say what the mode of being of qualities and actions is, and
it would have been the same had our illustrations been drawn from any
other "categories. " Hence the central and special problem of First
Philosophy is to analyse the notion of substance and to show the causes
of the existence of substances.

Next, we have to note that the word "substance" itself has two senses.
When we spoke of substance as one of the categories we were using it in
a secondary sense. We meant by substances "horse," "man," and the rest
of the "real kinds" which we find in Nature, and try to reproduce in a
scientific classification. In this sense of the word "substances" are a
special class of _predicates_, as when we affirm of Plato that he is a
man, or of Bucephalus that he is a horse. But in the primary sense a
substance means an absolutely individual thing, "_this_ man," or "_this_
horse. " We may therefore define primary substances from the logician's
point of view by saying that they can be only subjects of predication,
never predicates. Or again, it is peculiar to substances, that while
remaining numerically one a substance admits of incompatible
determinations, as Socrates, remaining one and the same Socrates, is
successively young and old. This is not true of "qualities," "actions,"
and the rest. The same colour cannot be first white and then black; the
same act cannot be first bad and then good. Thus we may say that
individual substances are the fixed and permanent factors in the world
of mutability, the invariants of existence. Processes go on in them,
they run the gamut of changes from birth to decay, processes take place
_among_ them, they act on and are acted on by one another, they
fluctuate in their qualities and their magnitude, but so long as a
substance exists it remains numerically one and the same throughout all
these changes. Their existence is the first and most fundamental
condition of the existence of the universe, since they are the bearers
of all qualities, the terms of all relations, and the agents and
patients in all interaction.

The point to note is that Aristotle begins his investigation into the
structure of What Is and the causes by which it is produced by starting
from the existence of individual things belonging to the physical order
and perceived by the senses. About any such thing we may ask two
questions, (1) into what constituent factors can it be logically
analysed? (2) and how has it come to exhibit the character which our
analysis shows it to have? The answer to these questions will appear
from a consideration of two standing antitheses which run through
Aristotle's philosophy, the contrast between Matter and Form, and that
between Potential and Actual, followed by a recapitulation of his
doctrine of the Four Causes, or four senses of the word Cause.

*Matter and Form*. --Consider any completely developed individual thing,
whether it is the product of human manufacture, as a copper bowl, or of
natural reproduction, as an oak-tree or a horse. We shall see at once
that the bowl is like other articles made of the same metal,
candlesticks, coal-vases, in being made of the same stuff, and unlike
them in having the special shape or structure which renders it fit for
being used as a bowl and not for holding a candle or containing coals.
So a botanist or a chemist will tell you that the constituent tissues of
an oak or horse, or the chemical elements out of which these tissues are
built up are of the same kind as those of an ash or an ox, but the oak
differs from the ash or the horse from the ox in characteristic
structure. We see thus that in any individual thing we can distinguish
two components, the stuff of which it consists--which may be identical
in kind with the stuff of which things of a very different kind
consist--and the structural law of formation or arrangement which is
peculiar to the "special" kind of thing under consideration. In the
actual individual thing these two are inseparably united; they do not
exist side by side, as chemists say the atoms of hydrogen and oxygen do
in a drop of water; the law of organisation or structure is manifested
in and through the copper, or the various tissues of the living body.
Aristotle expresses this by saying that you can distinguish two aspects
in an individual, its Matter, (_hyle, materia_) and its Form (_eidos,
forma_). The individual is the matter as organised in accord with a
determinate principle of structure, the form. Of these terms, the
former, _hyle_ (_materia_, matter) means literally timber, and more
specifically ship's timbers, and his selection of it to mean what is
most exactly rendered by our own word "stuff" may perhaps be due to a
reminiscence of an old Pythagorean fancy which looked on the universe as
a ship. The word for form is the same as Plato's, and its philosophical
uses are closely connected with its mathematical sense, "regular
figure," also a Pythagorean technicality which still survives in certain
stereotyped phrases in Euclid. Aristotle extends the analysis into
Matter and Form by analogy beyond the range of individual substances to
everything in which we can distinguish a relatively indeterminate
"somewhat" and a law or type of order and arrangement giving it
determination. Thus if you consider the relatively fixed or "formed"
character of a man in adult life, we may look upon this character as
produced out of the "raw material" of tendencies and dispositions, which
have received a specific development along definite lines, according to
the kind of training to which the mind has been subjected in the
"formative" period of its growth. We may therefore speak of native
disposition as the matter or stuff of which character is made, and the
practical problem of education is to devise a system of training which
shall impress on this matter precisely the form required if the grown
man is to be a good citizen of a good state. Since a man's character
itself is not a substance but a complex of habits or fixed ways of
reacting upon suggestions coming from the world around him, this is a
good instance of the extension of the antithesis of Matter and Form
beyond the category of substance. We see then that Matter in the
Aristotelian sense must not be confounded with body; the relatively
undetermined factor which receives completer determination by the
structural law or Form is Matter, whether it is corporeal or not. This
comes out with particular clearness in the metaphysical interpretation
put on the logical process of definition by genus and difference. When
I define any real kind by specifying a higher and wider class of which
it is a sub-kind, and adding the peculiar characteristics which
distinguish the sub-kind under consideration from the other sub-kinds of
the same genus, the genus may be said to stand to the "differences" as
Matter, the relatively indeterminate, to the Form which gives it its
structure.

We further observe that Matter and Form are strictly correlative. The
matter is called so relatively to the form which gives it further
determination. When the words are used in their strictest sense, with
reference to an individual thing, the Form is taken to mean the _last_
determination by which the thing acquires its complete character, and
the Matter is that which has yet to receive this last determination.
Thus in the case of a copper globe, the spherical figure is said to be
its Form, the copper its material. In the case of the human body, the
Matter is the various tissues, muscles, bones, skin, &c. But each of
these things which are counted as belonging to the Matter of the globe
or the human body has, according to Aristotle, a development behind it.
Copper is not an "element" but a specific combination of "elements," and
the same thing is even more true of the highly elaborate tissues of the
living body. Thus what is Matter relatively to the globe or living body
is Matter already determined by Form if we consider it relatively to its
own constituents. The so-called "elements" of Empedocles, earth, water,
air, fire, are the matter of all chemical compounds, the Form of each
compound being its specific law of composition; the immediate or
"proximate" Matter of the tissues of the animal body is, according to
Aristotle's biology, the "superfluous" blood of the female parent, out
of which the various tissues in the offspring are developed, and the
Matter of this blood is in turn the various substances which are taken
into the body of the parent as food and converted by assimilation into
blood. Their Matter, once more, is the earth, air, fire, and water of
which they are composed. Thus at every stage of a process of manufacture
or growth a fresh Form is superinduced on, or developed within, a Matter
which is already itself a combination of Matter and Form relatively to
the process by which it has itself been originated. Fully thought out,
such a view would lead to the conclusion that in the end the simple
ultimate matter of all individual things is one and the same throughout
the universe, and has absolutely no definite structure at all. The
introduction of Form or determinate structure of any kind would then
have to be thought of as coming from an outside source, since
structureless Matter cannot be supposed to give itself all sorts of
specific determinations, as has been demonstrated in our own times by
the collapse of the "Synthetic Philosophy. " Aristotle avoids the
difficulty by holding that "pure Matter" is a creation of our thought.
In actual fact the crudest form in which matter is found is that of the
"elements. " Since the transmutability of the "elements" is an
indispensable tenet in Aristotle's Physics, we cannot avoid regarding
earth, water, fire air as themselves determinations by specific Form of
a still simpler Matter, though this "prime Matter" "all alone, before a
rag of Form is on," is never to be found existing in its simplicity. [#]


[#] _Hudibras_, Pt. 1, Canto 1, 560.

"He had First Matter seen undressed;
He took her naked all alone,
Before one rag of Form was on. "


*The Potential and the Actual*. --So far we have been looking at the
analysis of the individual thing, as the current jargon puts it,
statically; we have arrived at the antithesis of Matter and Form by
contrasting an unfinished condition of anything with its finished
condition. But we may study the same contrast dynamically, with special
reference to the process of making or growth by which the relatively
undetermined or unfinished becomes determined or finished. The contrast
of Matter with Form then passes into the contrast between Potentiality
and Actuality. What this antithesis means we can best see from the case
of the growth of a living organism. Consider the embryos of two animals,
or the seeds of two plants. Even a botanist or a physiologist may be
unable to pronounce with certainty on the species to which the germ
submitted to him belongs, and chemical analysis may be equally at a
loss. Even at a later stage of development, the embryo of one
vertebrate animal may be indistinguishable from that of another. Yet it
is certain that one of two originally indistinguishable germs will grow
into an oak and the other into an elm, or one into a chimpanzee and the
other into a man. However indistinguishable, they therefore may be said
to have different latent tendencies or possibilities of development
within them. Hence we may say of a given germ, "though this is not yet
actually an oak, it is potentially an oak," meaning not merely that, if
uninterfered with, it will in time be an oak, but also that by no
interference can it be made to grow into an elm or a beech. So we may
look upon all processes of production or development as processes by
which what at first possessed only the tendency to grow along certain
lines or to be worked up into a certain form, has become actually
endowed with the character to which it possessed the tendency. The
acorn becomes in process of time an actual oak, the baby an actual man,
the copper is made into an actual vase, right education brings out into
active exercise the special capacities of the learner. Hence the
distinction between Matter and Form may also be expressed by saying that
the Matter is the persistent underlying _substratum_ in which the
development of the Form takes place, or that the individual when finally
determined by the Form is the Actuality of which the undeveloped Matter
was the Potentiality. The process of conception, birth, and growth to
maturity in Nature, or of the production of a finished article by the
"arts" whose business it is to "imitate" Nature, may be said to be one
of continuous advance towards the actual embodiment of a Form, or law of
organisation, in a Matter having the latent potentiality of developing
along those special lines. When Aristotle is speaking most strictly he
distinguishes the process by which a Form is realised, which he calls
Energeia, from the manifestation of the realised Form, calling the
latter Entelechy (literally "finished" or "completed" condition).
Often, however, he uses the word Energeia more loosely for the actual
manifestation of the Form itself, and in this he is followed by the
scholastic writers, who render Energeia by _actus_ or _actus purus_.

One presupposition of this process must be specially noted. It is not an
unending process of development of unrealised capacities, but always has
an End in the perfectly simple sense of a last stage. We see this best
in the case of growth. The acorn grows into the sapling and the sapling
into the oak, but there is nothing related to the oak as the oak is to
the sapling. The oak does not grow into something else. The process of
development from potential to actual in this special case comes to an
end with the emergence of the mature oak. In the organic world the end
or last state is recognised by the fact that the organism can now
exercise the power of reproducing its like. This tendency of organic
process to culminate in a last stage of complete maturity is the key to
the treatment of the problem of the "true end" of life in Aristotle's
_Ethics_.

*The Four Causes*. --The conception of the world involved in these
antitheses of Form and Matter, Potential and Actual, finds its fullest
expression in Aristotle's doctrine of the Four Causes or conditions of
the production of things. This doctrine is looked on by Aristotle as
the final solution of the problem which had always been the central one
for Greek philosophy, What are the causes of the world-order? All the
previous philosophies he regards as inadequate attempts to formulate the
answer to this question which is only given completely by his own
system. Hence the doctrine requires to be stated with some fullness.
We may best approach it by starting from the literal meaning of the
Greek terms _aitia_, _aition_, which Aristotle uses to convey the notion
of cause. _Aition_ is properly an adjective used substantially, and
means "that on which the legal responsibility for a given state of
affairs can be laid. " Similarly _aitia_, the substantive, means the
"credit" for good or bad, the legal "responsibility," for an act. Now
when we ask, "what is responsible for the fact that such and such a
state of things now exists? " there are four partial answers which may be
given, and each of these corresponds to one of the "causes. " A complete
answer requires the enumeration of them all. We may mention (1) the
_matter_ or _material_ cause of the thing, (2) the law according to
which it has grown or developed, the _form_ or _formal_ cause, (3) the
agent with whose initial impulse the development began--the
"starting-point of the process," or, as the later Aristotelians call it,
the _efficient_ cause, (4) the completed result of the whole process,
which is present in the case of human manufacture as a preconceived idea
determining the maker's whole method of handling his material, and in
organic development in Nature as implied in and determining the
successive stages of growth--the _end_ or _final_ cause. If any one of
these had been different, the resultant state of things would also have
been different. Hence all four must be specified in completely
accounting for it. Obvious illustrations can be given from artificial
products of human skill, but it seems clear that it was rather
reflection on the biological process of reproduction and growth which
originally suggested the analysis. Suppose we ask what was requisite in
order that there should be now an oak on a given spot. There must have
been (1) a germ from which the oak has grown, and this germ must have
had the latent tendencies towards development which are characteristic
of oaks. This is the material cause of the oak. (2) This germ must
have followed a definite law of growth; it must have had a tendency to
grow in the way characteristic of oaks and to develop the structure of
an oak, not that of a plane or an ash. This is form or formal cause.
(3) Also the germ of the oak did not come from nowhere; it grew on a
parent oak. The parent oak and its acorn-bearing activity thus
constitute the _efficient_ cause of the present oak. (4) And there must
be a final stage to which the whole process of growth is relative, in
which the germ or sapling is no longer becoming but is an adult oak
bearing fresh acorns. This is the _end_ of the process. One would not
be going far wrong in saying that Aristotle's biological cast of thought
leads him to conceive of this "end" in the case of reproduction as a
sub-conscious purpose, just as the workman's thought of the result to be
attained by his action forms a conscious directing purpose in the case
of manufacture. Both in Nature and in "art" the "form," the "efficient
cause," and the "end" tend to coalesce. Thus in Nature "a man begets a
man," organic beings give birth to other organic beings of the same
kind, or, in the technical language of the Aristotelian theory of
Causation, the efficient cause produces, as the "end" of its action, a
second being having the same "form" as itself, though realised in
different "matter," and numerically distinct from itself. Thus the
efficient cause (_i. e. _ the parent) is a "form" realised in matter, and
the "end" is the same "form" realised in other matter. So in "products
of art" the true "source of the process" is the "form" the realisation
of which is the "end" or final cause, only with this difference, that as
efficient cause the "form" exists not in the material but by way of
"idea" or "representation" in the mind of the craftsman. A house does
not produce another house, but the house as existing in "idea" in the
builder's mind sets him at work building, and so produces a
corresponding house in brick or stone. Thus the ultimate opposition is
between the "cause as matter," a passive and inert substratum of change
and development and the "formal" cause which, in the sense just
explained, is one with both the "efficient" or starting-point, and the
"end" or goal of development. It will, of course, be seen that
individual bearers of "forms" are indispensable in the theory; hence the
notion of _activity_ is essential to the causal relation. It is a
relation between things, not between events. Aristotle has no sense of
the word cause corresponding to Mill's conception of a cause as an event
which is the uniform precursor of another event.

Two more remarks may be made in this connection. (1) The prominence of
the notion of "end" gives Aristotle's philosophy a thorough-going
"ideological" character. God and Nature, he tells us, do nothing
aimlessly. We should probably be mistaken if we took this to mean that
"God and Nature" act everywhere with conscious design. The meaning is
rather that every natural process has a last stage in which the "form"
which was to begin with present in the agent or "source of change" is
fully realised in the matter in which the agent has set up the process
of change. The normal thing is _e. g. _ for animals to reproduce "their
kind"; if the reproduction is imperfect or distorted, as in monstrous
births, this is an exception due to the occasional presence in "matter"
of imperfections which hinder the course of development, and must be
regarded as "contrary to the normal course of Nature. " So hybrid
reproduction is exceptional and "against Nature," and this is shown by
the sterility of hybrids, a sort of lesser monstrosity. Even females,
being "arrested developments," are a sort of still minor deviation from
principle. (2) It may just be mentioned that Aristotle has a
classification of efficient causes under the three heads of Nature,
Intelligence (or Man), and Chance. The difference between Nature and
Man or Intelligence as efficient causes has already been illustrated.
It is that in causation by Nature, such as sexual reproduction, or the
assimilation of nutriment, or the conversion of one element into another
in which Aristotle believed, the form which is superinduced on the
matter by the agent already exists in the agent itself as _its_ form.