organs from which they emanate, yet the inquiry
reverts to nutrition as a fact ; without reference,
that is, either to vital processes or to food. We
may assume that Aristotle was unacquainted with
the rudimentary forms and development of the
corporeal organs, and yet, judging from this exor-
dium, he seems to have perceived that every part
must advance from a nascent state to its perfected
condition; and thus he has suggested the teaching
of developmental anatomy. As the inquiry proceeds,
we are reminded of the obscurity or inaccuracy of
language, in portraying the impressions upon and
the functions, so to say, of the sentient organs
even now the external object is, with us, in common
parlance, a sensible object ; sensation, besides its own
PEELUDE TO CHAP. IV. 75
sense, implies casual feelings from within ; sight
signifies both faculty and function ; and nourish-
ment is food as well as digestion. It is somewhat,
pei'haps, objectionable that Aristotle should have
bound up, so to say, the generative with the nutri-
tive function, seeing how they differ both in the
periods of development and duration ; they are
equally necessary, no doubt, to nature's design, but
still they are neither contemporaneous nor identical.
With respect to spontaneous generation here alluded
to Aristotle 1 admitted its possibility, and for obvious
reasons, in the case of eels j and, although he denied
that all mullets (TOUC K6<rTpe?e (j)ve<r6ai Trai/Tas) are
so reproduced, yet he believed that some of the
species spring forth (^U'CTOJ) from the mud and sand
on the sea-shore ; and thus it is evident, he continues,
that some creatures, not being derived from others,
may be the product of spontaneous generation. This
opinion upon reproduction prevailed for many ages,
and even yet, perhaps, notwithstanding the advance-
ment of science, it may not be altogether discredited.
1 Hist. Ani. vi. 14. 14. 15. 3.
CHAPTER IV.
IT is necessary, in order well to study those faculties,
that we should comprehend what each of them indi-
vidually is, and then, in like manner, carry our inquiry
into their consequences and other conditions. But if
it behove us to say what each of them is, as what is
the cogitative, sentient, or appetitive faculty, it should
previously be settled what that is which thinks and
that which feels ; for energies and acts are, abstract-
edly considered, pre-existent to their functions. Grant-
ing, however, that it is so, and that we ought, before
the faculties or functions, to have considered their
opposites, it might be fitting here also, and for the
same reason, first to define the opposites of the func-
tions define, that is, food before nutrition ; the object
before perception ; and the intelligible before thought.
Thus we must first speak upon nutrition and
generation, for the nutritive faculty is innate in other
beings besides animals ; it is the primal and most
universal influence of the Vital Principle, and through
it life is manifested in all beings. Its functions are
to generate and to employ nourishment ; for the most
CH. IV.] ARISTOTLE ON THE VITAL PRINCIPLE. 77
natural of the functions in beings which are perfect,
that is, which are neither dwarfed nor spontaneously
generated, is to produce another such as itself, an
animal an animal, and a plant a plant, in order that
they may partake, to the extent which has been
allotted to them, of the Everlasting and the Divine.
All creatures yearn after this, and, for the sake of it,
they do all that they do naturally ; but since such
beings cannot, in uninterrupted continuity, partake of
the Everlasting and the Divine, because no perishable
being can abidingly continue as one and the same ;
yet each can partake thereof in its own allotted por-
tion, be it larger or smaller, and still continue, if not
the same, like the same, and one, if not in number, as
species.
The Vital Principle is the cause and the origin of
a living body. Now, cause and origin have several
significations ; for the Vital Principle is equally a
cause, according to any one of the three defined modes
of causation : as that whence motion proceeds ; as
that for which motion is produced ; and cause, again,
as the essence of living bodies. It is evident that it
is a cause as an essence, since the essence is in all
things the cause of their being what they are ; and
as life is the mode of being in living beings, so Vital
Principle is the cause and the origin of all such. It
is the realizing principle, besides, the cause that is of
something which exists in potentiality becoming a
78 ARISTOTLE ON THE [BK. II.
reality. It is manifest, too, that Vital Principle is a
cause, in the sense of a final cause ; for as the mind
acts for some end, so does nature, and that end is her
aim ; and such an aim has the Vital Principle, by its
nature, in living bodies. Thus, all natural bodies,
those of animals as well as those of plants, are its
instruments, and are what they are for its purposes.
The term final cause has a twofold signification, as
it implies that for which, as well as that by which,
any result is obtained; and Vital Principle is a, final
cause, as that whence locomotion is derived, although
this is a property which does not belong to all living
creatures. Change and growth, moreover, are depen-
dent upon Vital Principle ; for sensation seems to be
a change of some kind, and whatever is sentient has
Vital Principle ; and this applies equally to growth
and decay, for nothing grows or decays naturally
unless it be nourished, and nothing is nourished which
does not partake of life. Empedocles has not ex-
pressed himself happily upon this point, as, after other
observations, he adds that plants take growth down-
wards, where they strike root, from this being the
natural direction of earth, and upwards, from this
being the natural direction of fire. Neither has he
clearly seized the import of the terms upwards and
downwards, as they are not identical for all creatures,
or for the universe ; for the nead is to animals what
the roots are to plants, if we may speak of organs
CH. IV.] VITAL PRINCIPLE. 79
after their functions, although in other respects dif-
ferent. But, besides these objections, what is that
which is to hold fire and earth, with their opposing
tendencies, together ? Now, unless there be a restrain-
ing force, they must be torn asunder, and if such
there be, it ought to be regarded as Vital Principle,
and the cause both of nourishment and growth.
The nature of fire seems, to some philosophers, to
be the absolute cause of nutrition as well as growth,
and that because it alone, among bodies or elements,
appears to be nourished and to grow. It might,
therefore, be assumed, that it is fire which works out
those processes in plants and animals ; but although
fire is possibly a joint cause, it cannot be the exclusive
cause, as this must be assigned rather to the Vital
Principle. The increase of fire is infinite, so long as
there is any thing combustible, but to all the bodies
of nature's constitution there is a limit and a relation
both as to bulk and increase ; and these are conditions,
not of fire but of Vital Principle ; not of matter but
of design.
Since the same faculty of Vital Principle is at
once nutritive and generative, it is necessary first to
define nutrition ; for it is by this, compared with other
faculties, that Vital Principle is especially distin-
guished. Nutrition, then, appears to be a contrary
acted upon by a contrary, but this does not imply any
kind of contrary by any other contrary ; it refers only
80 ARISTOTLE ON THE [BK. II.
to such contraries as can generate from and give
growth to one another. Thus, there are many things
derived from one another which are not always quan-
tities, as the healthy, for instance, is derived from the
unhealthy ; neither do these contraries appear, in any
manner, to be nourishment for one another, as water,
for instance, is nourishment for fire, but fire is not
nourishment for water. It is in homogeneous bodies
especially, that the contraries seem to be in the rela-
tions of nourishment and nourished. But here there
is a difficulty ; for while some maintain that like is
nourished as it is increased by like, there are others
who maintain, as we have said, that it is contrary
which is nourished by contrary ; that like is unim-
pressionable by like ; that food undergoes change and
is digested, and that all -change implies conversion to
an opposite or an intermediate state. Nourishment,
besides, is affected by the body which is nourished,
although the body is not affected by the nourishment,
just as the material is affected by the artisan, although
he is not affected by the material ; for it is the artisan
alone who converts the material from a raw state into
one of usefulness. There is, however, a distinction to
be observed in nourishment, between its last and ad-
ventitious or its first state ; if both states are nourish-
ment, distinguished only by the one being undigested,
and the other digested, then it may be correct to
admit of both explanations for nutrition; for in so
CH. IV.] VITAL PRINCIPLE. 81
far as food is undigested, it is contrary nourished by
contrary, and in so far as it is digested, it is like
nourished by like. Thus, it is manifest that both
these opinions are in one sense right, and in another
wrong. But as nothing can be nourished which does
not partake of life, so a living body may be regarded
as a body which is nourished from having life ; and
thus nutrition is not in a casual, but a positive rela-
tion to a living body. There is an obvious distinc-
tion between nourishment and growth : in so far as a
living body is quantity, it is capable of growth, and in
so far as a something is matter and essence, it is nourish-
ment ; for it preserves the essence of the body, which
exists so long as it can be nourished. Nourishment,
however, does not generate that which is nourished,
as it is the same as it ; for it is already itself the
essence, and nothing can generate, although it may
preserve itself. Thus, it is the same faculty of Vital
Principle which is able to preserve that, such as it
may be, which contains it, and it is nourishment
which renders it fit for its office ; and, therefore, when
deprived of nourishment, it can exist no longer.
Now, there are here three things or conditions
something to be nourished, something by which
nourished, and something which nourishes. That
which nourishes is the primal or nutritive faculty ;
that which is nourished is the body ; and that by
which nourished is food. And as things are correctly
6
82 ARISTOTLE ON THE VITAL PRINCIPLE. [BK. II.
designated after the object to which they tend, and
as the object here is to generate another like itself,
so the primal faculty may be set down as being
generative of another like itself. That "by which
nourished" has a twofold signification, as has that
by which a vessel is steered, and which implies hand
and rudder, of which the one only moves, while the
latter both moves and is moved. It is necessary to
nutrition that food should admit of being digested,
and as it is heat which works out digestion, so all
living creatures have heat.
It has thus then be shewn, although but super-
ficially, what nutrition is ; but the subject shall be
further elucidated in other treatises upon the subject.
PKELUDE TO CHAPTER V.
ARISTOTLE, having fully inquired into the process of nutri-
tion, here enters upon the investigation of the sensi-
bility or sentient system, which is, as he said, the
line of separation between animal and vegetable
existence ; the inquiry includes, of course, the senses
and their organs, as well as allusions to those ex-
ternal forces or qualities which by their action pro-
duce simultaneous perception, that is, sensation.
Sensibility is one of the great mysteries of our
mortal nature, but its investigation was, in that age,
additionally complicated and abstruse, as the brain
as well as its relation to the spinal cord and con-
nexion with the organs of the senses were unknown.
But, although anatomy has detected the links between
the brain and sentient organs, and thus shewn that
the senses are emanations, so to say, from it, yet this
knowledge, however otherwise valuable, does not
explain how matter has been constituted thus to
produce sensation, and, by reflexion, consciousness.
62
CHAPTER V.
LET us now proceed, as those subjects have been
scrutinized, to speak upon sensation in its widest
acceptation.
Sensation is the combined result, as has been said,
of a motion and an impression, for it seems to be some
kind of change ; and some writers maintain that it is
only like which is impressionable by like, but we
have already, in our treatises " upon action and im-
pression" shewn how far the opinion is or is not
tenable. But it is difficult to understand why there is
no sensation from the senses of themselves, that is,
why, without the presence of external objects, the
senses do not give out sensation, although fire, earth,
and the other elements, from which or the accidents
of which sensation is derived, are present in them. It
is evident that it is because the sensibility is not in a
state of activity, but is only in potentiality; and,
therefore, that it is with it as with a combustible ma-
terial, which alone, without something on fire, does
not burn ; for otherwise it might set fire to itself, and
would stand in no need of fire, in reality, for the purpose.
Since we speak of sentient perception in a two-fold
CH. V.] ARISTOTLE ON THE VITAL PRINCIPLE. 85
sense, (for we speak of one who hears and sees, in po-
tentiality, as " one hearing and seeing," although he
may happen to be asleep, and we say the same of
one who is actually employing those senses,) so may
sensation be spoken of in two ways, as subsisting in
potentiality and subsisting in activity. Let us, how-
ever, before proceeding further, observe that impres-
sion, motion, and action are for us equivalent terms
for motion is a kind of action, although an action
which is incomplete, as has been elsewhere explained.
Now, all things which are impressed and set in motion
are so affected by something capable of making im-
pression and existing in activity; so that impression
is in one sense by like, and in another sense by un-
like, as we have said for the unlike is subject to
impression, but, having been impressed, it is con-
verted into like. A distinction, however, must be
drawn between the terms potentiality and reality, for
we are now going to employ them in an absolute
sense any individual whatever, then, may be learned,
as we might speak of any man as learned, because
man is among beings capable of learning and being
learned ; and so we speak of a man as learned, from
his actually professing, at the time, grammatical or
other knowledge.
Thus, each of these individuals is learned in po-
tentiality, although in a different manner the one
is so because he is of a certain genus and peculiar
86 ARISTOTLE ON THE [BK. IT.
matter; and the other, because he can when he will
reflect upon his knowledge, provided there is no ex-
ternal impediment to his doing so. It is this one only,
however, when actually reflecting upon his know-
ledge, being in activity, and fully acquainted with
some one subject, as A. for instance, who is to be ac-
counted learned in reality. Both those first men, in
fact, are learned in potentiality; but the one is so
from having been modified by learning, and under-
gone frequent changes from one habit to an opposite
one; and the other is so from possessing sensibility
or rudimentary learning, and being able, although in
a different manner, to pass from inertia to activity.
But the term impression is not absolute in signifi-
cation, as sometimes it implies a kind of destruction
by a contrary, and sometimes it signifies rather pre-
servation of something being \n. potentiality by some-
thing which is in reality and like, in the relation that
potentiality bears to reality. Thus, the possession of
knowledge implies the power of reflecting upon it,
and this either is not change, being but an increase of
knowledge and a step towards its completion, or it is
change of a different kind. It is not correct, there-
fore, to say that an individual, when thinking, is un-
dergoing change, any more than that a builder, when
employed in building, is undergoing change; so that
the process by which an individual passes, as to his
thinking and reflecting faculties, from potentiality to
CH. V.] VITAL PRINCIPLE. 87
reality, ought to have some other appellation than
that of instruction. We may not then, as has been
observed, say of the individual who, from being in
potentiality, learns and receives knowledge from one
who is in reality and able to teach, that he suffers
impression, or else it must be admitted that there are
two modes of change, one in privative dispositions,
and another over habits and nature. The first change,
however, of this kind in the sentient being comes
from the parent at the moment of conception; as
from that moment the being has, as it were, learning
and sensibility. There is an analogy between the
state of activity and reflexion just alluded to, but
with this difference, that the impressions productive
of activity, as the audible, the visible, and others, are
all derived from without; and the cause of this is
that sensation, in activity, is employed upon particu-
lars, knowledge upon universals ; and universals are,
in some way, in the Vital Principle itself. The act
of thinking, therefore, is dependant only upon the will
of the individual, which is not the case with sentient
perception, as for it there must of necessity be ob-
jects to be perceived; and this holds good, and for
the same reason, with respect to the sciences which
are engaged upon external objects, because all such
objects are among particulars, and are external to the
percipient. But an opportunity may hereafter present
itself for the further elucidation of the subject.
88 ARISTOTLE ON THE VITAL PRINCIPLE. [BK. II.
Let it, for the present, suffice to say, that the
expression being in potentiality has not an absolute
signification, for it may be understood of a boy as
being qualified potentially to be a General, and also
of an individual of suitable age for the office ; and the
term sensibility is subject to like modifications of
meaning. But as the distinction between these two
states of sensibility is without any special appellation,
although it has been shewn that there is a distinction
between them and what the distinction is, it has been
found necessary to employ the terms impression and
change, as if their signification were unequivocal ; but,
as has been said, the sentient principle is, when in
potentiality, analogous to the external object when in
reality.
The sentient principle, in fact, suffers impression
when unlike; but, having been impressed, it is con-
verted into like, and becomes the same as that by
which the impression is made.
PRELUDE TO CHAPTER VI.
THIS chapter, adopting a former suggestion, commences
with the nature and influences of the objects and
properties which act upon the senses. As those pro-
perties or influences, however, whatever their denomi-
nation, light, sound, odour, savour, motion, number
<kc., are considered in their relation to the senses,
respectively, they here are merely characterized under
the terms, which are defined, of peculiar and common.
Casual or chance perception is exemplified by a figure
which is far from being apparent.
CHAPTER VI.
LET us, before proceeding further, speak upon the ob-
jects of perception in relation to each of the senses.
The object of perception is spoken of in a three-fold
manner, as there are two ways in which we speak of
perceiving objects distinctly, and one in which we
speak of perceiving them accidentally; and of those
two ways one signifies the property which is peculiar
to each sense, and the other the property which is
common to all the senses. I mean by peculiar pro-
perty that which cannot be perceived by any other
than its own sense, and concerning which that sense
cannot be deceived as colour for sight, sound for
hearing, and savour for taste. The touch, indeed,
discriminates several differences of quality, but every
other sense distinguishes only its own subjects ; and
thus sight or hearing is never deceived as to whether it
is colour or sound which is seen or heard, although it
may be deceived as to what or where the coloured,
what or where the sonorous body may be.
Such then the properties which are said to be
peculiar and to belong to particular senses ; but there
CH. VI.] ARISTOTLE ON THE VITAL PRINCIPLE. 91
are properties, such as motion, rest, number, form and
magnitude, which are termed common, as they belong
not to any one sense, but to all in common. Thus,
there is a movement which is perceptible both by
Touch and Sight. An object is said to be perceived
accidentally when, for example, something white
may be the Son of Diares for the percipient is sen-
sible of the individual accidentally, because of his
being an accident of that which is perceived; and,
therefore, no impression is made by that which is
perceived, as a special object, upon the percipient.
The properties of bodies, which are in them-
selves perceptible, are, strictly speaking, peculiar
properties ; and to such each particular sense is natu-
rally and essentially related.
PRELUDE TO CHAPTER VII.
THE treatise commences the examination of the senses
with the Sight, and closes with the Touch, which is
somewhat contrary to Aristotle's estimate of their
relative importance ; for he has shewn that the Touch
is the first, as it is the most universal of all the
senses, as well as essential to animal existence. Thus,
this sense is to sentient creatures what nutrition is
to other beings ; for as without Touch there can be
no animal, so without nutrition there can be no life.
Descartes, more in accordance with Aristotle's teach-
ing, begins with the Touch, and then proceeds to the
Taste, Smell, Hearing and Sight ; and so Grant ' makes
" all the other senses to be but modifications of the
Touch." Cuvier, however, reverses this it may be
general order, and treats of the special senses before
the Touch. It may be well to observe, that the
senses as well as their modes of excitation, had been
1 Outlines of Comp. Anat. e. vi.
PRELUDE TO CHAP. VII. 93
treated of in a distinct work ', which may be regarded
as supplementary to the present treatise ; and this
will explain why the eye and vision are here very
briefly alluded to, while particular attention has
there been given to the ear and hearing.
CHAPTER VII.
THE visible is that for which vision is the sense, and
the visible is both colour and something which is de-
scribable by words, although it happens to be without
a name; but our meaning will become clear to those
who accompany us in the inquiry. The visible is
colour, and colour is that which is upon something
visible in itself; and this something is visible, not
only after its appellation but, because it has in itself
the cause of being visible. All colour is motive of
the diaphanous, in activity, and to be so motive is the
nature of colour. On which account nothing is visi-
ble without light, but the colour of each object is
visible in the light; and we must, therefore, first say
what light is. There is a something diaphanous, and
I call diaphanous what is visible, and yet not visible,
1 De Sentu et Sens. i. 10.
94 AEISTOTLE ON THE [BK. II.
strictly speaking, in itself, but made visible by colour,
which is foreign to it. Such is air, and water, and
many solid bodies; yet neither air nor water, as air or
water, is diaphanous, but the same nature is present
in both those elements, which is in the eternal super-
nal body. Light is the active state of that same dia-
pkanous, in so far as it is diaphanous, and darkness is
the same in its state of potentiality. But light is the
colour, as it were, of the diaphanous, when made dia-
phanous in reality by fire, or other such element as
the supernal body; for to it belongs a something
which is identical with fire. We have thus said what
is the diaphanous and what light, and have shewn
that neither of them is fire, nor a body, strictly speak-
ing, nor an emanation from a body, (as, in that case,
they would be corporeal), but that they are the pre-
sence in the diaphanous of fire or something analogous