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.