Timaeus
flesh. The brain, the containing vessel of the divine part of the
soul, is (nearly) in the form of a globe, which is the image of
the gods, who are the stars, and of the universe.
There is, however, an inconsistency in Plato’s manner of
conceiving the soul of man; he cannot get rid of the element of
necessity which is allowed to enter. He does not, like Kant,
attempt to vindicate for men a freedom out of space and time; but
he acknowledges him to be subject to the influence of external
causes, and leaves hardly any place for freedom of the will. The
lusts of men are caused by their bodily constitution, though they
may be increased by bad education and bad laws, which implies
that they may be decreased by good education and good laws. He
appears to have an inkling of the truth that to the higher nature
of man evil is involuntary. This is mixed up with the view which,
while apparently agreeing with it, is in reality the opposite of
it, that vice is due to physical causes. In the Timaeus, as well
as in the Laws, he also regards vices and crimes as simply
involuntary; they are diseases analogous to the diseases of the
body, and arising out of the same causes. If we draw together the
opposite poles of Plato’s system, we find that, like Spinoza, he
combines idealism with fatalism.
The soul of man is divided by him into three parts, answering
roughly to the charioteer and steeds of the Phaedrus, and to the
(Greek) of the Republic and Nicomachean Ethics. First, there is
the immortal nature of which the brain is the seat, and which is
akin to the soul of the universe. This alone thinks and knows and
is the ruler of the whole. Secondly, there is the higher mortal
soul which, though liable to perturbations of her own, takes the
side of reason against the lower appetites. The seat of this is
the heart, in which courage, anger, and all the nobler affections
are supposed to reside. There the veins all meet; it is their
centre or house of guard whence they carry the orders of the
thinking being to the extremities of his kingdom. There is also a
third or appetitive soul, which receives the commands of the
immortal part, not immediately but mediately, through the liver,
which reflects on its surface the admonitions and threats of the
reason.
The liver is imagined by Plato to be a smooth and bright
substance, having a store of sweetness and also of bitterness,
which reason freely uses in the execution of her mandates. In
this region, as ancient superstition told, were to be found
intimations of the future. But Plato is careful to observe that
although such knowledge is given to the inferior parts of man, it
requires to be interpreted by the superior. Reason, and not
enthusiasm, is the true guide of man; he is only inspired when he
is demented by some distemper or possession. The ancient saying,
that ‘only a man in his senses can judge of his own actions,’ is
approved by modern philosophy too. The same irony which appears
in Plato’s remark, that ‘the men of old time must surely have
known the gods who were their ancestors, and we should believe
them as custom requires,’ is also manifest in his account of
divination.
The appetitive soul is seated in the belly, and there imprisoned
like a wild beast, far away from the council chamber, as Plato
graphically calls the head, in order that the animal passions may
not interfere with the deliberations of reason. Though the soul
is said by him to be prior to the body, yet we cannot help seeing
that it is constructed on the model of the body—the threefold
division into the rational, passionate, and appetitive
corresponding to the head, heart and belly. The human soul
differs from the soul of the world in this respect, that it is
enveloped and finds its expression in matter, whereas the soul of
the world is not only enveloped or diffused in matter, but is the
element in which matter moves. The breath of man is within him,
but the air or aether of heaven is the element which surrounds
him and all things.
Pleasure and pain are attributed in the Timaeus to the suddenness
of our sensations—the first being a sudden restoration, the
second a sudden violation, of nature (Phileb.). The sensations
become conscious to us when they are exceptional. Sight is not
attended either by pleasure or pain, but hunger and the appeasing
of hunger are pleasant and painful because they are
extraordinary.
Section 6.
I shall not attempt to connect the physiological speculations of
Plato either with ancient or modern medicine. What light I can
throw upon them will be derived from the comparison of them with
his general system.
There is no principle so apparent in the physics of the Timaeus,
or in ancient physics generally, as that of continuity. The world
is conceived of as a whole, and the elements are formed into and
out of one another; the varieties of substances and processes are
hardly known or noticed. And in a similar manner the human body
is conceived of as a whole, and the different substances of
which, to a superficial observer, it appears to be composed—the
blood, flesh, sinews—like the elements out of which they are
formed, are supposed to pass into one another in regular order,
while the infinite complexity of the human frame remains
unobserved. And diseases arise from the opposite process—when the
natural proportions of the four elements are disturbed, and the
secondary substances which are formed out of them, namely, blood,
flesh, sinews, are generated in an inverse order.
Plato found heat and air within the human frame, and the blood
circulating in every part. He assumes in language almost
unintelligible to us that a network of fire and air envelopes the
greater part of the body. This outer net contains two lesser
nets, one corresponding to the stomach, the other to the lungs;
and the entrance to the latter is forked or divided into two
passages which lead to the nostrils and to the mouth. In the
process of respiration the external net is said to find a way in
and out of the pores of the skin: while the interior of it and
the lesser nets move alternately into each other. The whole
description is figurative, as Plato himself implies when he
speaks of a ‘fountain of fire which we compare to the network of
a creel.’ He really means by this what we should describe as a
state of heat or temperature in the interior of the body. The
‘fountain of fire’ or heat is also in a figure the circulation of
the blood. The passage is partly imagination, partly fact.
He has a singular theory of respiration for which he accounts
solely by the movement of the air in and out of the body; he does
not attribute any part of the process to the action of the body
itself. The air has a double ingress and a double exit, through
the mouth or nostrils, and through the skin. When exhaled through
the mouth or nostrils, it leaves a vacuum which is filled up by
other air finding a way in through the pores, this air being
thrust out of its place by the exhalation from the mouth and
nostrils. There is also a corresponding process of inhalation
through the mouth or nostrils, and of exhalation through the
pores. The inhalation through the pores appears to take place
nearly at the same time as the exhalation through the mouth; and
conversely. The internal fire is in either case the propelling
cause outwards—the inhaled air, when heated by it, having a
natural tendency to move out of the body to the place of fire;
while the impossibility of a vacuum is the propelling cause
inwards.
Thus we see that this singular theory is dependent on two
principles largely employed by Plato in explaining the operations
of nature, the impossibility of a vacuum and the attraction of
like to like. To these there has to be added a third principle,
which is the condition of the action of the other two,—the
interpenetration of particles in proportion to their density or
rarity. It is this which enables fire and air to permeate the
flesh.
Plato’s account of digestion and the circulation of the blood is
closely connected with his theory of respiration. Digestion is
supposed to be effected by the action of the internal fire, which
in the process of respiration moves into the stomach and minces
the food. As the fire returns to its place, it takes with it the
minced food or blood; and in this way the veins are replenished.
Plato does not enquire how the blood is separated from the
faeces.
Of the anatomy and functions of the body he knew very
little,—e.g. of the uses of the nerves in conveying motion and
sensation, which he supposed to be communicated by the bones and
veins; he was also ignorant of the distinction between veins and
arteries;—the latter term he applies to the vessels which conduct
air from the mouth to the lungs;—he supposes the lung to be
hollow and bloodless; the spinal marrow he conceives to be the
seed of generation; he confuses the parts of the body with the
states of the body—the network of fire and air is spoken of as a
bodily organ; he has absolutely no idea of the phenomena of
respiration, which he attributes to a law of equalization in
nature, the air which is breathed out displacing other air which
finds a way in; he is wholly unacquainted with the process of
digestion. Except the general divisions into the spleen, the
liver, the belly, and the lungs, and the obvious distinctions of
flesh, bones, and the limbs of the body, we find nothing that
reminds us of anatomical facts. But we find much which is derived
from his theory of the universe, and transferred to man, as there
is much also in his theory of the universe which is suggested by
man. The microcosm of the human body is the lesser image of the
macrocosm. The courses of the same and the other affect both;
they are made of the same elements and therefore in the same
proportions. Both are intelligent natures endued with the power
of self-motion, and the same equipoise is maintained in both. The
animal is a sort of ‘world’ to the particles of the blood which
circulate in it. All the four elements entered into the original
composition of the human frame; the bone was formed out of smooth
earth; liquids of various kinds pass to and fro; the network of
fire and air irrigates the veins. Infancy and childhood is the
chaos or first turbid flux of sense prior to the establishment of
order; the intervals of time which may be observed in some
intermittent fevers correspond to the density of the elements.
The spinal marrow, including the brain, is formed out of the
finest sorts of triangles, and is the connecting link between
body and mind. Health is only to be preserved by imitating the
motions of the world in space, which is the mother and nurse of