No More Learning

Thus he distinguishes the following varieties of "motion":
_generation_ (the coming of an individual thing into being), with its
opposite _decay_ or _corruption_ (the passing of a thing out of being),
_alteration_ (change of _quality_ in a thing), _augmentation_ and
_diminution_ (change in the _magnitude_ of a thing), _motion through
space_ (of which latter he recognises two sub-species, rectilinear
_transference_ and _rotation_ in a circular orbit about an axis). It is
this last variety, motion through space, which is the most fundamental
of all, since its occurrence is involved in that of any of the other
types of process mentioned, though Aristotle does not hold the
thorough-going mechanical view that the other processes are only
apparent, and that, as we should put it, qualitative change is a mere
disguise which mechanical motion wears for our senses.

*The Eternity of Motion*. --Certain very important consequences follow
from the conception of efficient causation which we have been
describing. Aristotle has no sympathy with the "evolutionist" views
which had been favoured by some of his predecessors. According to his
theory of organic generation, "it takes a man to beget a man "; where
there is a baby, there must have been a father. Biological kinds
representing real clefts in Nature, the process of the production of a
young generation by an already adult generation must be thought of as
without beginning and without end. There can be no natural "evolution"
of animals of one species from individuals of a different kind. Nor
does it occur to Aristotle to take into account the possibility of
"Creationism," the sudden coming into being of a fully fledged first
generation at a stroke. This possibility is excluded by the doctrine
that the "matter" of a thing must exist beforehand as an indispensable
condition of the production of that thing. Every baby, as we said, must
have had a father, but that father must also have been a baby before he
was a full-grown man. Hence the perpetuation of unchanging species must
be without beginning and without end. And it is implied that all the
various processes, within and without the organism, apart from which its
life could not be kept up, must be equally without beginning and without
end. The "cosmos," or orderly world of natural processes, is strictly
"eternal"; "motion" is everlasting and continuous, or unbroken. Even
the great Christian theologians who built upon Aristotle could not
absolutely break with him on this point. St. Thomas, though obliged to
admit that the world was actually created a few thousand years before
his own time, maintains that this can only be known to be true from
revelation, philosophically it is equably tenable that the world should
have been "created from all eternity. " And it is the general doctrine
of scholasticism that the expression "creation" only denotes the
absolute dependence of the world on God for its being. When we say "God
created the world out of nothing," we mean that He did not make it out
of pre-existing matter, that it depends for its being on Him only; the
expression is purely negative in its import.

*God*. --With the doctrine of the eternity of the world and the processes
which make up its life we come close to the culminating theory of
Aristotelian First Philosophy, its doctrine of God, as the eternal,
unchanging source of all change, movement, and process. All motion is a
process within matter by which the forms latent in it are brought into
actual manifestation. And the process only takes place in the presence
of an adequate efficient cause or source of motion. Hence the eternity
of natural processes involves the existence of one or more eternal
sources of motion. For, if we do not admit the existence of an
unoriginated and ever-present source or sources of motion, our only
alternative is to hold that the world-process is due to a series of
sources of motion existing successively. But such a view would leave the
unity and unbroken continuity of the world-process unaccounted for. It
would give us a succession of processes, temporally contiguous, not one
unbroken process. Hence we argue from the continuity of motion to its
dependence on a source or sources which are permanent and present
throughout the whole everlasting world-process. And when we come to the
question whether there is only one such ultimate source of movement for
the whole universe, or several, Aristotle's answer is that the supreme
"Unmoved Mover" is one. One is enough for the purpose, and the law of
parcimony forbids us to assume the superfluous. This then is the
Aristotelian conception of God and God's relation to the world. God is
the one supreme unchanging being to whose presence the world responds
with the whole process of cosmic development, the ultimate educer of the
series of "forms" latent in the "matter" of the world into actual
manifestation. Standing, as He does, outside the whole process which by
His mere presence He initiates in Nature, He is not himself a composite
of "form" and "matter," as the products of development are. He is a pure
individual "form" or "actuality," with no history of gradual development
behind it. Thus He is a purely immaterial being, indispensable to the
world's existence but transcending it and standing outside it. _How_
His presence inspires the world to move Aristotle tries to explain by
the metaphor of appetition. Just as the good I desire and conceive,
without itself "moving" "moves" my appetition, so God moves the universe
by being its good. This directly brings about a uniform unbroken
rotation of the whole universe round its axis (in fact, the alternation
of day and night). And since this rotation is communicated from the
outermost "sphere" of heaven to all the lesser "spheres" between it and
the immovable centre, the effects of God's presence are felt
universally. At the same time, we must note that though God is the
supreme Mover of the Universe, He is not regarded by Aristotle as its
Creator, even in the sense in which creation can be reconciled with the
eternity of the world. For the effect of God's presence is simply to
lead to the development of "form" in an already existing "matter. "
Without God there could be no "form" or order in things, not even as
much as is implied in the differentiation of matter into the four
"elements," yet "primary matter" is no less than God a precondition of
all that happens.

It is characteristic of Aristotle that his God is as far from
discharging the functions of a Providence as He is from being a Creator.
His "activity" is not, as Plato had made it, that of the great "Shepherd
of the sheep. " As far as the world is concerned, God's only function is
to be there to move its appetition. For the rest, the unbroken activity
of this life is directed wholly inward. Aristotle expressly calls it an
"activity of immobility. " More precisely, he tells us, it is activity
of thought, exercised unbrokenly and everlastingly upon the only object
adequate to exercise God's contemplation, Himself. His life is one of
everlasting _self_-contemplation or "thinking of thought itself. " Like
all unimpeded exercise of activity, it is attended by pleasure, and as
the activity is continuous, so the pleasure of it is continuous too. At
our best, when we give ourselves up to the pure contemplative activity
of scientific thought or aesthetic appreciation, we enter for a while
into this divine life and share the happiness of God. But that is a
theme for our chapter on the _Ethics_.

It is a far cry from this conception of a God untroubled by care for a
world to which He is only related as the object of its aspiration to the
God who cares even for the fall of the sparrow and of whom it is
written, _Sic Deus dilexit mundum_, but it was the standing task of the
philosophical theologians of the Middle Ages to fuse the two
conceptions. Plato's God, who, if not quite the Creator, is the "Father
and Fashioner" of us all, and keeps providential watch over the world He
has fashioned, would have lent Himself better to their purposes, but
Plato was held by the mediaeval church to have denied the resurrection of
the body. The combination of Aristotle's Theism with the Theism of
early Christianity was effected by exquisitely subtle logical devices,
but even in St. Thomas one cannot help seeing the seams.

Nor can one help seeing in Aristotle's own doctrine the usual want of
coherence between an initial anti-Platonic bias and a final reversion to
the very Platonic positions Aristotle is fond of impugning. We are told
at the outset that the Platonic "separate forms" are empty names, and
that the real individual thing is always a composite of matter and a
form which only exists "in matter. " We find in the end that the source
of the whole process by which "matter" becomes imbued with "form" is a
being which is "pure" form and stands outside the whole development
which its presence sets up. And the issue of Aristotle's warning against
"poetic metaphors" is the doctrine that God moves the world by being
"the object of the world's desire. "




*CHAPTER IV*

*PHYSICS*


There is no part of Aristotle's system which has been more carefully
thought out than his Physics; at the same time it is almost wholly on
account of his physical doctrines that his long ascendancy over thought
is so much to be regretted. Aristotle's qualifications as a man of
science have been much overrated. In one department, that of descriptive
natural history, he shows himself a master of minute and careful
observation who could obtain unqualified praise from so great a
naturalist as Darwin. But in Astronomy and Physics proper his
inferiority in mathematical thinking and his dislike for mechanical ways
of explaining facts put him at a great disadvantage, as compared with
Plato and Plato's Pythagorean friends. Thus his authority was for
centuries one of the chief influences which prevented the development of
Astronomy on right lines. Plato had himself both taught the mobility of
the earth and denied correctly that the earth is at the centre of the
universe, and the "Copernican" hypothesis in Astronomy probably
originated in the Academy. Aristotle, however, insists on the central
position of the earth, and violently attacks Plato for believing in its
motion. It is equally serious that he insists on treating the so-called
"four elements" as ultimately unanalysable forms of matter, though Plato
had not only observed that so far from being the ABC (_stoicheia_ or
_elementa_, literally, letters of the alphabet) of Nature they do not
deserve to be called even "syllables," but had also definitely put
forward the view that it is the geometrical structure of the
"corpuscles" of body upon which sensible qualities depend. It is on
this doctrine, of course, that all mathematical physics rests.
Aristotle reverts to the older theory that the differences between one
"element" and another are qualitative differences of a sensible kind.
Even in the biological sciences Aristotle shows an unfortunate proneness
to disregard established fact when it conflicts with the theories for
which he has a personal liking. Thus, though the importance of the
brain as the central organ of the sensori-motor system had been
discovered in the late sixth or early fifth century by the physician
Alemacon of Crotona, and taught by the great Hippocrates in the fifth
and by Plato in the fourth century, Aristotle's prejudices in favour of
the doctrines of a different school of biologists led him to revert to
the view that it is the heart which is the centre of what we now call
the "nervous system. " It is mainly on account of these reactionary
scientific views that he was attacked in the early seventeenth century
by writers like our own Francis Bacon, who found in veneration for
Aristotle one of the chief hindrances to the free development of natural
science. The same complaints had been made long before by critics
belonging to the Platonic Academy. It is a Platonist of the time of
Marcus Aurelius who sums up a vigorous attack on the Aristotelian
astronomy by the remark that Aristotle never understood that the true
task of the physicist is not to prescribe laws to Nature, but to learn
from observation of the facts what the laws followed by Nature are.

In determining the scope of Physics, we have to begin by considering
what is the special characteristic of things produced by Nature as
contrasted with those produced by "art. " The obvious distinction,
intimated by the very etymology of the word "Nature" (_physis_,
connected with _phyesthai_, to grow, to be born, as _natura_ is with
_nasci_), is that "what is by Nature" is born and grows, whereas what is
as a result of artifice is _made_. The "natural" may thus be said to
consist of living bodies and of their constituent parts. Hence
inorganic matter also is included in "Nature," on the ground that living
tissue can be analysed back into compounds of the "elements. " Now
things which are alive and grow are distinguished from things which are
made by "a source of motion and quiescence within themselves"; all of
them exhibit motions, changes of quality, processes of growth and
decline which are initiated from within. Hence Nature may be defined as
the totality of things which have a source of motion internal to
themselves and of the constituent parts of such things. Nature then
comprises all beings capable of spontaneous change. Whatever either does
not change at all, or only changes in consequence of external
influences, is excluded from Nature.

Thus the fundamental fact everywhere present in Nature is "change,"
"process," "motion. " Since motion in the literal sense of change of
position is involved as a condition of every such process, and such
motion requires space through which to move and time to move in, the
doctrine of space and time will also form part of Physics. Hence a
great part of Aristotle's special lectures on Physics is occupied with
discussion of the nature of space and time, and of the continuity which
we must ascribe to them if the "continuous motion" on which the unbroken
life of the universe depends is to be real Aristotle knows nothing of
the modern questions whether space and time are "real" or only
"phenomenal," whether they are "objective" or "subjective. " Just as he
simply assumes that bodies are things that really exist, whether we
happen to perceive them or not, so he assumes that the space and time in
which they move are real features of a world that does not depend for
its existence on our perceiving it.

His treatment of space is singularly _naif_. He conceives it as a sort
of vessel, into which you can pour different liquids. Just as the same
pot may hold first wine and then water, so, if you can say, "there was
water here, but now there is air here," this implies the existence of a
receptacle which once held the water, but now holds the air. Hence a
jug or pot may be called a "place that can be carried about," and space
or place may be called "an immovable vessel. " Hence the "place" of a
thing may be defined as the boundary, or inner surface, of the body
which immediately surrounds the thing. It follows from this that there
can be no empty space. In the last resort, "absolute space" is the
actual surface of the outermost "heaven" which contains everything else
in itself but is not contained in any remoter body. Thus all things
whatever are "in" this "heaven. " But it is not itself "in" anything
else. In accord with the standing Greek identification of determinate
character with limitation, Aristotle holds that this outermost heaven
must be at a limited distance from us. Actual space is thus finite in
the sense that the volume of the universe could be expressed as a finite
number of cubic miles or yards, though, since it must be "continuous,"
it is infinitely divisible. However often you subdivide a length, an
area, or a volume, you will always be dividing it into lesser lengths,
&c. , which can once more be divided. You will never by division come to
"points," _i. e. _ mere positions without magnitude of divisibility.

The treatment of time is more thoughtful. Time is inseparably connected
with movement or change. We only perceive that time has elapsed when we
perceive that change has occurred. But time is not the same as change.
For change is of different and incommensurate kinds, change of place,
change of colour, &c. ; but to take up time is common to all these forms
of process. And time is not the same as motion. For there are
different rates of speed, but the very fact that we can compare these
different velocities implies that there are not different velocities of
_time_. Time then is that in terms of which we _measure_ motion, "the
number of motion in respect of before and after," _i. e. _ it is that by
which we estimate the _duration_ of processes. Thus _e. g. _ when we
speak of _two_ minutes, _two_ days, _two_ months as required for a
certain process to be completed, we are counting something. This
something is time. It does not seem to occur to Aristotle that this
definition implies that there are indivisible bits of time, though he
quite correctly states the incompatible proposition that time is "made
up of successive _nows_," _i. e. _ moments which have no duration at all,
and can no more be counted than the points on a straight line. He
recognises of course that the "continuity" of motion implies that of
time as well as of space. Since, however, "continuity" in his language
means the same thing as indefinite divisibility, it ought not to be
possible for him to regard time as "made up of _nows_"; time, like
linear extension, ought for him to be a "length of" something.

*The Continuous Motion and the "Spheres. "*--The continuous world-process
depends upon a continuous movement set up in the universe as a whole by
the presence of an everlasting and unchangeable "First Mover," God.
From the self-sameness of God, it follows that this most universal of
movements must be absolutely uniform. Of what precise kind can such a
movement be? As the source of the movement is one, and the object moved
is also one--viz. the compass of the "heaven," the movement of the
_primum mobile_ or "first moved"--the object immediately stimulated to
motion by God's presence to it, must be mechanically simple. Now
Aristotle, mistakenly, held that there are two forms of movement which
are simple and unanalysable, motion of translation along a straight
line, and motion of rotation round an axis. He is at pains to argue
that rectilinear motion, which we easily discover to be that
characteristic of bodies near the earth's surface when left to
themselves, cannot be the kind of movement which belongs to the "heaven"
as a whole. For continuous rectilinear movement in the same direction
could not go on for ever on his assumption that there is no space
outside the "heaven," which is itself at a finite distance from us. And
motion to and fro would not be unbroken, since Aristotle argues that
every time a moving body reached the end of its path, and the sense of
its movement was reversed, it would be for two consecutive moments in
the same place, and therefore at rest. Reversal of sense would imply a
discontinuity. Hence he decides that the primary unbroken movement must
be the rotation of the "first moved"--that is, the heaven containing the
fixed stars--round its axis. This is the only movement which could go
on for ever at a uniform rate and in the same sense. Starting with the
conviction that the earth is at rest in the centre of the universe, he
inevitably accounts for the alternation of day and night as the effect
of such a revolution of the whole universe round an axis passing through
the centre of the earth. The universe is thus thought of as bounded by
a spherical surface, on the concave side of which are the fixed stars,
which are therefore one and all at the same distance from us. This
sphere, under the immediate influence of God, revolves on its axis once
in twenty-four hours, and this period of revolution is absolutely
uniform. Next the apparently irregular paths of the "planets" known to
Aristotle (_i. e. _ the moon, Mercury, Venus, the sun, Mars, Jupiter,
Saturn) are resolved into combinations of similar uniform rotations,
each planet having as many "spheres" assigned to it as are requisite for
the analysis of its apparent path into perfectly circular elementary
motions. Altogether Aristotle holds that fifty-four such rotating
spheres are required over and above the "first moved" itself, whose
rotation is, of course, communicated to all the lesser "spheres"
included within it. As in the case of the "first moved," the uniform
unceasing rotation of each "sphere" is explained by the influence on it
of an unchanging immaterial "form," which is to its own "sphere" what
God is to the universe as a whole. In the Aristotelianism of the
mediaeval church these pure forms or intelligences which originate the
movements of the various planetary spheres are naturally identified with
angels. It is _e. g. _ to the angelic intelligences which "move" the
heaven of Venus, which comes third in order counting outward from the
earth, that Dante addresses his famous Canzone, _Voi ch' intendendo il
terzo del movete_. The mediaeval astronomy, however, differs in two
important respects from that of Aristotle himself. (1) The number of
"spheres" is different. Increasing knowledge of the complexity of the
paths of the planets showed that if their paths are to be analysed into
combinations of circular motions, fifty-four such rotations must be an
altogether inadequate number. Aristotle's method of analysis of the
heavenly movements was therefore combined with either or both of two
others originated by pure astronomers who sat loose to metaphysics. One
of these methods was to account for a planet's path by the introduction
of _epicycles_. The planet was thought of not as fixed at a given point
on its principal sphere, but as situated on the circumference of a
lesser sphere which has its centre at a fixed point of the principal
sphere and rotates around an axis passing through this centre. If need
were, this type of hypothesis could be further complicated by imagining
any number of such epicycles within epicycles. The other method was the
employment of "eccentrics," _i. e. _ circular movements which are
described not about the common centre of the earth and the universe, but
about some point in its neighbourhood. By combinations of epicycles and
eccentrics the mediaeval astronomers contrived to reduce the number of
principal spheres to _one_ for each planet, the arrangement we find in
Dante. (2) Also real or supposed astronomical perturbations unknown to
Aristotle led some mediaeval theorists to follow the scheme devised by
Alphonso the Wise of Castille, in which further spheres are inserted
between that of Saturn, the outermost planet, and the "first moved. " In
Dante, we have, excluding the "empyrean" or immovable heaven where God
and the blessed are, nine "spheres," one for each of the planets, one
for the fixed stars, and one for the "first moved," which is now
distinguished from the heaven of the stars. In Milton, who adopts the
"Alphonsine" scheme, we have further a sphere called the "second
movable" or "crystalline" introduced between the heaven of the fixed
stars and the "first moved," to account for the imaginary phenomenon of
"trepidation. "[#] In reading Dante, Shakespeare, and Milton, we have
always to remember that none of these reproduces the Aristotelian
doctrine of the "spheres" accurately; their astronomy is an amalgam of
Aristotle, Ptolemy, and Hipparchus.


[#] _Paradise Lost_, iii. 481.

"They pass the planets seven, and pass the fixed,
And that crystalline sphere whose balance weighs
The trepidation talked, and that first moved. "


So far, the doctrine of the fifty-five "spheres" might be no more than a
legitimate mathematical fiction, a convenient device for analysing the
complicated apparent movements of the heavenly bodies into circular
components. This was originally the part played by "spheres" in ancient
astronomical theory, and it is worth while to be quite clear about the
fact, as there is a mistaken impression widely current to-day that
Aristotle's astronomy is typical of Greek views in general. The truth
is that it is peculiar to himself. The origin of the theory was
Academic. Plato proposed to the Academy as a subject of inquiry, to
devise such a mathematical analysis of astronomical motions as will best
"save the appearances," _i. e. _ will most simply account for the apparent
paths of the planets. The analysis of these paths into resultants of
several rotations was offered as a solution by the astronomer Eudoxus of
Cnidus. So far, the "spheres," then, were a mere mathematical
hypothesis. What Aristotle did, and it is perhaps the most retrograde
step ever taken in the history of a science, was to convert the
mathematical hypothesis into physical fact. The "spheres" become with
him real bodies, and as none of the bodies we are familiar with exhibit
any tendency to rotate in circles when left to themselves, Aristotle was
forced to introduce into Physics the disastrous theory, which it was a
great part of Galileo's life-work to destroy, that the stuff of which
the spheres are made is a "fifth body," different from the "elements" of
which the bodies among which we live are made. Hence he makes an
absolute distinction between two kinds of matter, "celestial matter,"
the "fifth body," and "terrestrial" or "elementary" matter. The
fundamental difference is that "terrestrial" or "elementary" matter,
left to itself, follows a rectilinear path, "celestial" matter rotates,
but it is further inferred from the supposed absolute uniformity of the
celestial movements that "celestial matter" is simple, uncompounded,
incapable of change, and consequently that no new state of things can
ever arise in the heavens. The spheres and planets have always been and
will always be exactly as they are at the present moment. Mutability is
confined to the region of "terrestrial" or "elementary" matter, which
only extends as far as the orbit of the moon, the "lowest of the
celestial bodies," because it is only "terrestrial" things which are, as
we should say, chemical compounds. This is the doctrine which Galileo
has in mind when he dwells on such newly-discovered astronomical facts
as the existence of sun-spots and variable stars, and the signs of
irregularity presented by the moon's surface. The distinction is
peculiar to Aristotle. No one before him had ever thought of supposing
the heavenly bodies to be made of any materials other than those of
which "bodies terrestrial" are made. In the Academic attack on
Aristotle's science of which we have already spoken the two points
singled out for reprobation are (1) his rejection of the principle that
all moving bodies, left to themselves, follow a rectilinear path, and
(2) his denial that the heavenly bodies are made of the same "elements"
as everything else. (It may just be mentioned in passing that our word
_quintessence_ gets its sense from the supposed special "nobility" of
the incorruptible "fifth body. ")

*Terrestrial Bodies*. --As we have seen already, Aristotle was out of
sympathy with the tendency to regard the sensible differences between
bodies as consequences of more ultimate differences in the geometrical
structure of their particles. Hence his whole attitude towards the
problems of that branch of natural science which we call physics is
quite unlike any view to which we are accustomed. He reverts from the
mathematical lines of thought current in Plato's Academy to the type of
view more natural to the "plain man," and, like the earliest
sixth-century men of science, regards the _qualitative_ differences
which our senses apprehend as fundamental. Among these, particular
stress is laid on the difference in sensible temperature (the hot--the
cold), in saturation (the dry--the moist), and in density (the
dense--the rare). If we consider the first two of these oppositions, we
can make four binary combinations of the elementary "opposite"
characters, viz. hot and dry, hot and moist, cold and moist, cold and
dry. These combinations are regarded as corresponding respectively to
the sensible characteristics of the four bodies which Empedocles, the
father of Greek chemistry, had treated as the ultimate components of
everything. Fire is hot and dry, air hot and moist, water moist and
cold, earth cold and dry. This reflection shows us why Aristotle held
that the most rudimentary form in which "matter" ever actually exists is
that of one of these "elements. " Each of them has _one_ quality in
common with another, and it is in virtue of this that a portion of one
element can be assimilated by and transmuted into another, a process
which seems to the untutored eye to be constantly recurring in Nature.
We also observe that the order in which the "elements" appear, when so
arranged as to form a series in which each term has one quality in
common with each of its neighbours, is also that of their increasing
density. This would help to make the conception of their
transmutability all the more natural, as it suggests that the process
may be effected by steady condensation. We must remember carefully that
for Aristotle, who denies the possibility of a vacuum, as for the
mediaeval alchemists, condensation does not mean a mere diminution of the
distances between corpuscles which remain unchanged in character, but is
a process of real qualitative change in the body which undergoes it.
Incidentally we may remark that _all_ changes of quality are regarded by
Aristotle as stages in a continuous "movement" from one extreme of a
scale to another. For example, colours, with him as with Goethe, form a
series of which the "opposites" white and black are the end-points.
Every other colour is a combination of white and black according to a
definite proportion.

The Aristotelian doctrine of weight was one of the chief obstacles which
seventeenth-century science had to contend with in establishing correct
notions in dynamics. It is a curious feature of Greek science before
Aristotle that, though the facts connected with gravity were well known,
no one introduced the notion of weight to account for them. The
difference between heavy bodies and light bodies had been previously
treated as secondary for science. Plato's treatment of the matter is
typical of the best fourth-century science. We must not try to explain
why the heavier bodies tend to move towards the earth's surface by
saying that they have a "downward" motion; their motion is not downward
but "towards the centre" (the earth, though not fixed at the centre of
the universe, being nearer to it than the rest of the solar and sidereal
system). Plato then explains the tendency in virtue of which the
heavier bodies move towards the "centre" as an attraction of like for
like. The universal tendency is for smaller masses of "earth," "water,"
"air," "fire" to be attracted towards the great aggregations of the same
materials. This is far from being a satisfactory theory in the light of
facts which were not yet known to Plato, but it is on the right lines.
It starts from the conception of the facts of gravity as due to an
"attractive force" of some kind, and it has the great merit of bringing
the "sinking" of stones and the "rising" of vapours under the same
explanation.

Aristotle, though retaining the central idea that a body tends to move
towards the region where the great cosmic mass of the same kind is
congregated, introduced the entirely incompatible notion of an absolute
distinction of "up" and "down. " He identified the centre of the
universe with that of the earth, and looked on motion to this centre as
"downward. " This led him to make a distinction between "heavy" bodies,
which naturally tend to move "down," and "light" bodies, which tend to
move "up" away from the centre. The doctrine works out thus. The
heaviest elements tend to be massed together nearest the centre, the
lightest to be furthest from it. Each element thus has its "proper
place," that of water being immediately above earth, that of air next,
and that of fire furthest from the centre, and nearest to the regions
occupied by "celestial matter. " (Readers of Dante will recollect the
ascent from the Earthly Paradise through the "sphere of fire" with which
the _Paradiso_ opens. )

In its own "proper region" no body is heavy or light; as we should say
any fluid loses its weight when immersed in itself. When a portion of
an element is out of its own region and surrounded by the great cosmic
aggregate of another element, either of two cases may occur. The body
which is "out of its element" may be _below_ its proper place, in which
case it is "light" and tends to move perpendicularly upwards to its
place, or it may be _above_ its proper place, and then it is "heavy" and
tends to move perpendicularly "down" until it reaches its place. It was
this supposed real distinction between motion "up" and motion "down"
which made it so hard for the contemporaries of Galileo to understand
that an inflated bladder rises for the same reason that a stone sinks.

*Biology*. --Of Aristotle's biology reasons of space forbid us to say
much here. But a remark or two may be made about his theory of
reproduction, since it is constantly referred to in much modern
literature and has also played its part in theology. An interesting
point is the distinction between "perfect" and "imperfect" animals.
"Perfect" animals are those which can only be reproduced sexually.
Aristotle held, however, that there are some creatures, even among
vertebrates, which _may_ be produced by the vivifying effect of solar
heat on decomposing matter, without any parents at all. Thus
malobservation of the facts of putrefaction led to the belief that flies
and worms are engendered by heat from decaying bodies, and it was even
thought that frogs and mice are produced in the same way from
river-slime. In this process, the so-called "aequivocal generation,"
solar heat was conceived as the operative efficient cause which leads to
the realisation of an organic "form" in the decaying matter.

In sexual reproduction Aristotle regards the male parent as the agent or
efficient cause which contributes the element of form and organisation
to the offspring. The female parent supplies only the raw material of
the new creature, but she supplies the whole of this. No _material_ is
supplied by the male parent to the body of the offspring, a theory which
St. Thomas found useful in defending the dogma of the Virgin Birth.

*Psychology*. --Since the mind grows and develops, it comes under the
class of things which have a "source of motion internal to themselves,"
and psychology is therefore, for Aristotle, a branch of Physics. To
understand his treatment of psychological questions we need bear two
things in mind. (1) _Psyche_ or "soul" means in Greek more than
"consciousness" does to us. Consciousness is a relatively late and
highly developed manifestation of the principle which the Greeks call
"soul. " That principle shows itself not merely in consciousness but in
the whole process of nutrition and growth and the adaptation of motor
response to an external situation. Thus consciousness is a more
secondary feature of the "soul" in Greek philosophy than in most modern
thought, which has never ceased to be affected by Descartes' selection
of "thought" as the special characteristic of psychical life. In common
language the word _psyche_ is constantly used where we should say "life"
rather than "soul," and in Greek philosophy a work "on the _Psyche_"
means what we should call one on "the principle of life. "

(2) It is a consequence of this way of thinking of the "soul" that the
process of bodily and mental development is regarded by Aristotle as one
single continuous process. The growth of a man's intellect and
character by which he becomes a thinker and a citizen is a continuation
of the process by which his body is conceived and born and passes into
physical manhood. This comes out in the words of the definition of the
soul. "The soul is the first entelechy (or actual realisation) of a
natural organic body. " What this means is that the soul stands to the
living body as all form realised in matter does to the matter of which
it is the form, or that the soul is the "form" of the body. What the
"organic body" is to the embryo out of which it has grown, that soul is
to the body itself. As the embryo grows into the actual living body, so
the living body grows into a body exhibiting the actual directing
presence of mind. Aristotle illustrates the relation by the remark that
if the whole body was one vast eye, seeing would be its soul. As the
eye is a tool for seeing with, but a living tool which is part of
ourselves, so the body is a like tool or instrument for living with.
Hence we may say of the soul that it is the "end" of the body, the
activity to which the body is instrumental, as seeing is the "end" to
which the eye is instrumental. But we must note that the soul is called
only the "first" or initial "entelechy" of the body. The reason is that
the mere presence of the soul does not guarantee the full living of the
life to which our body is but the instrument. If we are to _live_ in
the fullest sense of the word, we must not merely "have" a soul; we
"have" it even in sleep, in ignorance, in folly. The soul itself needs
further to be educated and trained in intelligence and character, and to
exercise its intelligence and character efficiently on the problems of
thought and life. The mere "presence" of soul is only a first step in
the progress towards fullness of life. This is why Aristotle calls the
soul the _first_ entelechy of the living body. The full and final
entelechy is the life of intelligence and character actively
functioning.

From this conception of the soul's relation to the body we see that
Aristotle's "doctrine of body and mind" does not readily fall into line
with any of the typical theories of our time. He neither thinks of the
soul as a thing acting on the body and acted on by it, nor yet as a
series of "states of mind" concomitant with certain "states of body. "
From his point of view to ask whether soul and body interact, or whether
they exhibit "parallelism," would be much the same thing as to ask
whether life interacts with the body, or whether there is a
"parallelism" between vital processes and bodily processes. We must not
ask at all how the body and soul are united. They are one thing, as the
matter and the form of a copper globe are one. Thus they are in actual
fact inseparable. The soul is the soul of its body and the body the body
of its soul. We can only distinguish them by logical analysis, as we can
distinguish the copper from the sphericity in the copper globe.

*Grades of Psychical Life*. --If we consider the order of development, we
find that some vital activities make their appearance earlier than
others, and that it is a universal law that the more highly developed
activities always have the less highly developed as their basis and
precondition, though the less highly developed may exist apart from the
more highly developed. So we may arrange vital activities in general in
an ontogenetic order, the order in which they make their appearance in
the individual's development. Aristotle reckons three such stages, the
"nutritive," the "sensitive," and the "intelligent. " The lowest form in
which life shows itself at all, the level of minimum distinction between
the living and the lifeless, is the power to take in nutriment,
assimilate it, and grow. In vegetables the development is arrested at
this point. With the animals we reach the next highest level, that of
"sensitive" life. For all animals have at least the sense of touch.
Thus they all show sense-perception, and it is a consequence of this
that they exhibit "appetition," the simplest form of conation, and the
rudiments of feeling and "temper. " For what has sensations can also
feel pleasure and pain, and what can feel pleasure and pain can desire,
since desire is only appetition of what is pleasant. Thus in the
animals we have the beginnings of cognition, conation, and affective and
emotional life in general. And Aristotle adds that locomotion makes its
appearance at this level; animals do not, like plants, have to trust to
their supply of nutriment coming to them; they can go to it.

The third level, that of "intelligence," _i. e. _ the power to compare,
calculate, and reflect, and to order one's life by conscious rule, is
exhibited by man. What distinguishes life at this level from mere
"sensitive" life is, on the intellectual side, the ability to cognise
universal truths, on the conative, the power to live by rule instead of
being swayed by momentary "appetition. " The former gives us the
possibility of science, the latter of moral excellence. [#]


[#] _Cf. _ Dante's "Fatti non foste a viver como bruti,
Ma per seguir virtute e conosoenza. "


*Sensation*. --Life manifests itself at the animal level on the cognitive
side as sense-perception, on the conative as appetition or desire, on
the affective as feeling of pleasure or pain, and in such simple
emotional moods as "temper," resentment, longing. Aristotle gives
sensation a logical priority over the conative and emotional expression
of "animal" life. To experience appetition or anger or desire you must
have an object which you crave for or desire or are angry with, and it
is only when you have reached the level of presentations through the
senses that you can be said to have an object. Appetition or "temper"
is as real a fact as perception, but you cannot crave for or feel angry
with a thing you do not apprehend.

Aristotle's definition of sense perception is that it is a "capacity for
discerning" or distinguishing between "the sensible qualities of
things. " His conception of the process by which the discernment or
distinguishing is effected is not altogether happy. In sense-perception
the soul "takes into itself the _form_ of the thing perceived without
its _matter_, as sealing-wax receives the shape of an iron seal-ring
without the iron. " To understand this, we have to remember that for
Aristotle the sensible qualities of the external world, colour, tones,
tastes, and the rest, are not effects of mechanical stimulation of our
sense-organs, but real qualities of bodies. The hardness of iron, the
redness of a piece of red wax are all primarily "in" the iron or the
wax. They are "forms," or determinations by definite law, of the
"matter" of the iron or the wax. This will become clearer if we
consider a definite example, the red colour of the wax. In the wax the
red colour is a definite combination of the colour-opposites white and
black according to a fixed ratio. Now Aristotle's view of the process of
sense-perception is that when I become aware of the red colour the same
proportion of white to black which makes the wax red is reproduced in my
organ of vision; my eye, while I am seeing the red, "assimilated" to the
wax, is itself for the time actually "reddened. " But it does not become
wax because the red thing I am looking at is a piece of red wax. The
eye remains a thing composed of living tissues. This is what is meant
by saying that in seeing the colours of things the eye receives "forms"
without the "matter" of the things in which those forms are exhibited.
Thus the process of sense-perception is one in which the organ of sense
is temporarily assimilated to the thing apprehended in respect of the
particular quality cognised by that organ, but in respect of no other.
According to Aristotle this process of "assimilation" always requires
the presence of a "medium. " If an object is in immediate contact with
the eye we cannot see its colour; if it is too near the ear, we do not
discern the note it gives out. Even in the case of touch and taste
there is no immediate contact between the object perceived and the true
organ of perception. For in touch the "flesh" is not the organ of
apprehension but an integument surrounding it and capable of acting as
an intermediary between it and things. Thus perception is always
accomplished by a "motion" set up in the "medium" by the external
object, and by the medium in our sense-organs. Aristotle thus contrives
to bring correct apprehension by sense of the qualities of things under
the formula of the "right mean" or "right proportion," which is better
known from the use made of it in the philosopher's theory of conduct.
The colour of a surface, the pitch of the note given out by a vibrating
string, &c. , depend on, and vary with, certain forms or ratios "in" the
surface or the vibrating string; our correct apprehension of the
qualities depends on the reproduction of the _same_ ratios in our
sense-organs, the establishment of the "right proportion" in _us_. That
this "right proportion" may be reproduced in our own sense-organs it is
necessary (1) that the medium should have none of the sensible qualities
for the apprehension whereof it serves as medium, _e. g. _ the medium in
colour-perception must be colourless. If it had a colour of its own,
the "motion" set up by the coloured bodies we apprehend would not be
transmitted undistorted to our organs; we should see everything through
a coloured haze. It is necessary for the same reason (2) that the
percipient organ itself, when in a state of quiescence, should possess
none of the qualities which can be induced in it by stimulation. The
upshot of the whole theory is that the sense-organ is "potentially" what
the sense-quality it apprehends is actually. Actual perceiving is just
that special transition from the potential to the actual which results
in making the organ for the time being _actually_ of the same quality as
the object.

*The Common Sensibles and the Common Sense-organ*. --Every sense has a
range of qualities connected with it as its special objects. Colours
can only be perceived by the eye, sounds by the ear, and so forth. But
there are certain characters of perceived things which we appear to
apprehend by more than one sense. Thus we seem to perceive size and
shape either by touch or by sight, and number by hearing as well, since
we can count _e. g. _ the strokes of an unseen bell. Hence Aristotle
distinguishes between the "special sensible qualities" such as colour
and pitch, and what he calls the "common sensibles," the character of
things which can be perceived by more than one organ. These are
enumerated as size, form or shape, number, motion (and its opposite
rest), being. (The addition of this last is, of course, meant to account
for our conviction that any perceived colour, taste, or other quality is
a reality and not a delusion. ) The list corresponds very closely with
one given by Plato of the "things which the mind perceives _by herself
without the help of any organ_," _i. e. _ of the leading determinations of
sensible things which are due not to sense but to understanding. It was
an unfortunate innovation to regard the discernment of number or
movement, which obviously demand intellectual processes such as counting
and comparison, as performed immediately by "sense," and to assign the
apprehension of number, movement, figure to a central "organ. " This
organ he finds in the heart. The theory is that when the "special
organs" of the senses are stimulated, they in turn communicate movements
to the blood and "animal spirits" (_i. e. _ the vapours supposed to be
produced from the blood by animal heat). These movements are propagated
inwards to the heart, where they all meet. This is supposed to account
for the important fact that, though our sensations are so many and
diverse, we are conscious of our own unity as the subjects apprehending
all this variety. The unity of the perceiving subject is thus made to
depend on the unity of the ultimate "organ of sensation," the heart.
Further, when once a type of motion has been set up in any sense-organ
at the periphery of the body it will be propagated inward to the "common
sensorium" in the heart. The motions set up by stimulation, _e. g. _ of
the eye and of the skin, are partly different, partly the same (viz. in
so far as they are determined by the number, shape, size, movement of
the external stimuli). Hence in the heart itself the stimulation on
which perception of number or size depends is one and the same whether
it has been transmitted from the eye or from the skin! Awareness of
lapse of time is also regarded as a function of the "common
sense-organ," since it is the "common sensory" which perceives motion,
and lapse of time is apprehended only in the apprehension of motion.
Thus, in respect of the inclusion of geometrical form and lapse of time
among the "common sensibles," there is a certain resemblance between
Aristotle's doctrine and Kant's theory that recognition of spatial and
temporal order is a function not of understanding but of "pure" sense.
It is further held that to be aware that one is perceiving
(self-consciousness) and to discriminate between the different classes
of "special" sense-perception must also be functions of the "common
sense-organ. " Thus Aristotle makes the mistake of treating the most
fundamental acts of intelligent reflection as precisely on a par, from
the point of view of the theory of knowledge, with awareness of colour
or sound.

A more legitimate function assigned to the "common sensorium" in the
heart is that "fantasy," the formation of mental imagery, depends on its
activity. The simplest kind of "image," the pure memory-image left
behind after the object directly arousing perception has ceased to
stimulate, is due to the persistence of the movements set up in the
heart after the sensory process in the peripheral organ is over. Since
Aristotle denies the possibility of thinking without the aid of
memory-images, this function of the "common sensorium" is the
indispensable basis of mental recall, anticipation, and thought. Neither
"experience," _i. e. _ a general conviction which results from the
frequent repetition of similar perceptions, nor thought can arise in any
animal in which sense-stimulation does not leave such "traces" behind
it. Similarly "free imagery," the existence of trains of imagination
not tied down to the reproduction of an actual order of sensations, is
accounted for by the consideration that "chance coincidence" may lead to
the stimulation of the heart in the same way in which it might have been
stimulated by actual sensation-processes. Sleeping and waking and the
experiences of dream-life are likewise due to changes in the functioning
of the "common sense-organ," brought about partly by fatigue in the
superficial sense-organs, partly by qualitative changes in the blood and
"animal spirits" caused by the processes of nutrition and digestion.
Probably Aristotle's best scientific work in psychology is contained in
the series of small essays in which this theory of memory and its
imagery is worked out. (Aristotle's language about the "common
sensibles" is, of course, the source of our expression "common sense,"
which, however, has an entirely different meaning. The shifting of
sense has apparently been effected through Cicero's employment of the
phrase _sensus communis_ to mean tactful sympathy, the feeling of
fellowship with our kind on which the Stoic philosophers laid so much
stress. )

*Thought*. --Though thinking is impossible except by the use of imagery,
to think is not merely to possess trains of imagery, or even to be aware
of possessing them. Thinking means understanding the meaning of such
mental imagery and arriving through the understanding at knowledge of
the structure of the real world. How this process of interpreting
mental imagery and reaching valid truth is achieved with greater and
greater success until it culminates in the apprehension of the supreme
principles of philosophy we have seen in dealing with the Aristotelian
theory of knowledge. From the point of view of the "physicist" who is
concerned with thinking simply as a type of natural process, the
relation of "understanding" to the mental imagery just described is
analogous to that of sensation to sensible qualities. The objects which
thinking apprehends are the universal types of relation by which the
world of things is pervaded. The process of thinking is one in which
this system of universal relations is reproduced "by way of idea" in the
mind of the thinker. The "understanding" thus stands to its objects as
matter to form. The process of getting actually to understand the world
is one in which our "thought" or "understanding" steadily receives
completer determination and "form" from its contemplation of reality.
In this sense, the process is one in which the understanding may be said
to be passive in knowledge. It is passive because it is the subject
which, at every fresh stage in the progress to knowledge, is being quite
literally "informed" by the action of the real world through the
sensation and imagery. Hence Aristotle says that, in order that the
understanding may be correctly "informed" by its contact with its
objects, it must, before the process begins, have no determinate
character of its own. It must be simply a capacity for apprehending the
types of interconnection. "What is called the intelligence--I mean that
with which the soul thinks and understands--is not an actual thing until
it thinks. " (This is meant to exclude any doctrine which credits the
"understanding" with either _furniture_ of its own such as "innate
ideas," or a specific _structure_ of its own. If the results of our
thinking arose partly from the structure of the world of objects and
partly from inherent laws of the "structure of mind," our thought at its
best would not reproduce the universal "forms" or "types" of
interconnection as they really are, but would distort them, as the
shapes of things are distorted when we see them through a lens of high
refractive index. ) Thus, though Aristotle differs from the modern
empiricists in holding that "universals" realty exist "in" things, and
are the links of connection between them, he agrees with the empiricist
that knowledge is not the resultant of a combination of "facts" on the
one side and "fundamental laws of the mind's working" on the other. At
the outset the "understanding" has no structure; it develops a structure
for itself in the same process, and to the same degree, in which it
apprehends the "facts. " Hence the "understanding" only is real in the
actual process of understanding its objects, and again in a sense the
understanding and the things it understands are one. Only we must
qualify this last statement by saying that it is only "potentially" that
the understanding is the forms which it apprehends. Aristotle does not
mean by this that such things as horses and oxen are thoughts or
"ideas. " By the things with which "understanding" is said to be one he
means the "forms" which we apprehend when we actually understand the
world or any part of it, the truths of science. His point then is that
the actual thinking of these truths and the truths themselves do not
exist apart from one another. "Science" does not mean certain things
written down in a book; it means a mind engaged in thinking and knowing
things, and of the mind itself, considered out of its relation to the
actual life of thinking the truths of science, we can say no more than
that it is a name for the fact that we are capable of achieving such
thought.

*The Active Intelligence*. --So far Aristotle's account of thought has
been plain sailing. Thought has been considered as the final and
highest development of the vital functions of the organism, and hence as
something inseparable from the lower functions of nutrition and
sensitive life. The existence of a thought which is not a function of a
living body, and which is not "passive," has been absolutely excluded.
But at this point we are suddenly met by the most startling of all the
inconsistencies between the naturalistic and the "spiritualist" strains
in Aristotle's philosophy. In a few broken lines he tells us that there
is another sense of the word "thought" in which "thought" actually
creates the truths it understands, just as light may be said to make the
colours which we see by its aid. "And _this_ intelligence," he adds,
"is separable from matter, and impassive and unmixed, being in its
essential nature an _activity_. . . . It has no intermission in its
thinking. It is only in separation from matter that it is fully itself,
and it alone is immortal and everlasting . . . while the passive
intelligence is perishable and does not think at all, apart from this.