Timaeus
generation. The work of digestion is carried on by the superior
sharpness of the triangles forming the substances of the human
body to those which are introduced into it in the shape of food.
The freshest and acutest forms of triangles are those that are
found in children, but they become more obtuse with advancing
years; and when they finally wear out and fall to pieces, old age
and death supervene.
As in the Republic, Plato is still the enemy of the purgative
treatment of physicians, which, except in extreme cases, no man
of sense will ever adopt. For, as he adds, with an insight into
the truth, ‘every disease is akin to the nature of the living
being and is only irritated by stimulants.’ He is of opinion that
nature should be left to herself, and is inclined to think that
physicians are in vain (Laws—where he says that warm baths would
be more beneficial to the limbs of the aged rustic than the
prescriptions of a not over-wise doctor). If he seems to be
extreme in his condemnation of medicine and to rely too much on
diet and exercise, he might appeal to nearly all the best
physicians of our own age in support of his opinions, who often
speak to their patients of the worthlessness of drugs. For we
ourselves are sceptical about medicine, and very unwilling to
submit to the purgative treatment of physicians. May we not claim
for Plato an anticipation of modern ideas as about some questions
of astronomy and physics, so also about medicine? As in the
Charmides he tells us that the body cannot be cured without the
soul, so in the Timaeus he strongly asserts the sympathy of soul
and body; any defect of either is the occasion of the greatest
discord and disproportion in the other. Here too may be a
presentiment that in the medicine of the future the
interdependence of mind and body will be more fully recognized,
and that the influence of the one over the other may be exerted
in a manner which is not now thought possible.
Section 7.
In Plato’s explanation of sensation we are struck by the fact
that he has not the same distinct conception of organs of sense
which is familiar to ourselves. The senses are not instruments,
but rather passages, through which external objects strike upon
the mind. The eye is the aperture through which the stream of
vision passes, the ear is the aperture through which the
vibrations of sound pass. But that the complex structure of the
eye or the ear is in any sense the cause of sight and hearing he
seems hardly to be aware.
The process of sight is the most complicated (Rep.), and consists
of three elements—the light which is supposed to reside within
the eye, the light of the sun, and the light emitted from
external objects. When the light of the eye meets the light of
the sun, and both together meet the light issuing from an
external object, this is the simple act of sight. When the
particles of light which proceed from the object are exactly
equal to the particles of the visual ray which meet them from
within, then the body is transparent. If they are larger and
contract the visual ray, a black colour is produced; if they are
smaller and dilate it, a white. Other phenomena are produced by
the variety and motion of light. A sudden flash of fire at once
elicits light and moisture from the eye, and causes a bright
colour. A more subdued light, on mingling with the moisture of
the eye, produces a red colour. Out of these elements all other
colours are derived. All of them are combinations of bright and
red with white and black. Plato himself tells us that he does not
know in what proportions they combine, and he is of opinion that
such knowledge is granted to the gods only. To have seen the
affinity of them to each other and their connection with light,
is not a bad basis for a theory of colours. We must remember that
they were not distinctly defined to his, as they are to our eyes;
he saw them, not as they are divided in the prism, or
artificially manufactured for the painter’s use, but as they
exist in nature, blended and confused with one another.
We can hardly agree with him when he tells us that smells do not
admit of kinds. He seems to think that no definite qualities can
attach to bodies which are in a state of transition or
evaporation; he also makes the subtle observation that smells
must be denser than air, though thinner than water, because when
there is an obstruction to the breathing, air can penetrate, but
not smell.
The affections peculiar to the tongue are of various kinds, and,
like many other affections, are caused by contraction and
dilation. Some of them are produced by rough, others by
abstergent, others by inflammatory substances,—these act upon the
testing instruments of the tongue, and produce a more or less
disagreeable sensation, while other particles congenial to the
tongue soften and harmonize them. The instruments of taste reach
from the tongue to the heart. Plato has a lively sense of the
manner in which sensation and motion are communicated from one
part of the body to the other, though he confuses the affections
with the organs. Hearing is a blow which passes through the ear
and ends in the region of the liver, being transmitted by means
of the air, the brain, and the blood to the soul. The swifter
sound is acute, the sound which moves slowly is grave. A great
body of sound is loud, the opposite is low. Discord is produced
by the swifter and slower motions of two sounds, and is converted
into harmony when the swifter motions begin to pause and are
overtaken by the slower.
The general phenomena of sensation are partly internal, but the
more violent are caused by conflict with external objects.
Proceeding by a method of superficial observation, Plato remarks
that the more sensitive parts of the human frame are those which
are least covered by flesh, as is the case with the head and the
elbows. Man, if his head had been covered with a thicker pulp of
flesh, might have been a longer-lived animal than he is, but
could not have had as quick perceptions. On the other hand, the
tongue is one of the most sensitive of organs; but then this is
made, not to be a covering to the bones which contain the marrow
or source of life, but with an express purpose, and in a separate
mass.
Section 8.
We have now to consider how far in any of these speculations
Plato approximated to the discoveries of modern science. The
modern physical philosopher is apt to dwell exclusively on the
absurdities of ancient ideas about science, on the haphazard
fancies and a priori assumptions of ancient teachers, on their
confusion of facts and ideas, on their inconsistency and
blindness to the most obvious phenomena. He measures them not by
what preceded them, but by what has followed them. He does not
consider that ancient physical philosophy was not a free enquiry,
but a growth, in which the mind was passive rather than active,
and was incapable of resisting the impressions which flowed in
upon it. He hardly allows to the notions of the ancients the
merit of being the stepping-stones by which he has himself risen
to a higher knowledge. He never reflects, how great a thing it
was to have formed a conception, however imperfect, either of the
human frame as a whole, or of the world as a whole. According to
the view taken in these volumes the errors of ancient physicists
were not separable from the intellectual conditions under which
they lived. Their genius was their own; and they were not the
rash and hasty generalizers which, since the days of Bacon, we
have been apt to suppose them. The thoughts of men widened to
receive experience; at first they seemed to know all things as in
a dream: after a while they look at them closely and hold them in
their hands. They begin to arrange them in classes and to connect
causes with effects. General notions are necessary to the
apprehension of particular facts, the metaphysical to the
physical. Before men can observe the world, they must be able to
conceive it.
To do justice to the subject, we should consider the physical
philosophy of the ancients as a whole; we should remember, (1)
that the nebular theory was the received belief of several of the
early physicists; (2) that the development of animals out of
fishes who came to land, and of man out of the animals, was held
by Anaximander in the sixth century before Christ (Plut. Symp.
Quaest; Plac. Phil.); (3) that even by Philolaus and the early
Pythagoreans, the earth was held to be a body like the other
stars revolving in space around the sun or a central fire; (4)
that the beginnings of chemistry are discernible in the ‘similar
particles’ of Anaxagoras. Also they knew or thought (5) that
there was a sex in plants as well as in animals; (6) they were
aware that musical notes depended on the relative length or
tension of the strings from which they were emitted, and were
measured by ratios of number; (7) that mathematical laws pervaded
the world; and even qualitative differences were supposed to have
their origin in number and figure; (8) the annihilation of matter
was denied by several of them, and the seeming disappearance of
it held to be a transformation only. For, although one of these
discoveries might have been supposed to be a happy guess, taken
together they seem to imply a great advance and almost maturity
of natural knowledge.
We should also remember, when we attribute to the ancients hasty
generalizations and delusions of language, that physical
philosophy and metaphysical too have been guilty of similar
fallacies in quite recent times. We by no means distinguish
clearly between mind and body, between ideas and facts. Have not
many discussions arisen about the Atomic theory in which a point
has been confused with a material atom? Have not the natures of
things been explained by imaginary entities, such as life or
phlogiston, which exist in the mind only? Has not disease been
regarded, like sin, sometimes as a negative and necessary,
sometimes as a positive or malignant principle? The ‘idols’ of
Bacon are nearly as common now as ever; they are inherent in the
human mind, and when they have the most complete dominion over
us, we are least able to perceive them. We recognize them in the
ancients, but we fail to see them in ourselves.
Such reflections, although this is not the place in which to
dwell upon them at length, lead us to take a favourable view of
the speculations of the Timaeus. We should consider not how much
Plato actually knew, but how far he has contributed to the
general ideas of physics, or supplied the notions which, whether
true or false, have stimulated the minds of later generations in
the path of discovery. Some of them may seem old-fashioned, but