repeat what we said before, if the medium for touch were a membrane
separating us from the object without our observing its existence,
we should be relatively to it in the same condition as we are now to
air or water in which we are immersed; in their case we fancy we can
touch objects, nothing coming in between us and them. But there
remains this difference between what can be touched and what can be
seen or can sound; in the latter two cases we perceive because the
medium produces a certain effect upon us, whereas in the perception of
objects of touch we are affected not by but along with the medium;
it is as if a man were struck through his shield, where the shock is
not first given to the shield and passed on to the man, but the
concussion of both is simultaneous.
In general, flesh and the tongue are related to the real organs of
touch and taste, as air and water are to those of sight, hearing,
and smell. Hence in neither the one case nor the other can there be
any perception of an object if it is placed immediately upon the
organ, e.g. if a white object is placed on the surface of the eye.
This again shows that what has the power of perceiving the tangible is
seated inside. Only so would there be a complete analogy with all
the other senses. In their case if you place the object on the organ
it is not perceived, here if you place it on the flesh it is
perceived; therefore flesh is not the organ but the medium of touch.
What can be touched are distinctive qualities of body as body; by
such differences I mean those which characterize the elements, viz,
hot cold, dry moist, of which we have spoken earlier in our treatise
on the elements. The organ for the perception of these is that of
touch-that part of the body in which primarily the sense of touch
resides. This is that part which is potentially such as its object
is actually: for all sense-perception is a process of being so
affected; so that that which makes something such as it itself
actually is makes the other such because the other is already
potentially such. That is why when an object of touch is equally hot
and cold or hard and soft we cannot perceive; what we perceive must
have a degree of the sensible quality lying beyond the neutral
point. This implies that the sense itself is a 'mean' between any
two opposite qualities which determine the field of that sense. It
is to this that it owes its power of discerning the objects in that
field. What is 'in the middle' is fitted to discern; relatively to
either extreme it can put itself in the place of the other. As what is
to perceive both white and black must, to begin with, be actually
neither but potentially either (and so with all the other
sense-organs), so the organ of touch must be neither hot nor cold.
Further, as in a sense sight had for its object both what was
visible and what was invisible (and there was a parallel truth about
all the other senses discussed), so touch has for its object both what
is tangible and what is intangible. Here by 'intangible' is meant
(a) what like air possesses some quality of tangible things in a
very slight degree and (b) what possesses it in an excessive degree,
as destructive things do.
We have now given an outline account of each of the several senses.
12
The following results applying to any and every sense may now be
formulated.
(A) By a 'sense' is meant what has the power of receiving into
itself the sensible forms of things without the matter. This must be
conceived of as taking place in the way in which a piece of wax
takes on the impress of a signet-ring without the iron or gold; we say
that what produces the impression is a signet of bronze or gold, but
its particular metallic constitution makes no difference: in a similar
way the sense is affected by what is coloured or flavoured or
sounding, but it is indifferent what in each case the substance is;
what alone matters is what quality it has, i.e. in what ratio its
constituents are combined.
(B) By 'an organ of sense' is meant that in which ultimately such
a power is seated.
The sense and its organ are the same in fact, but their essence is
not the same. What perceives is, of course, a spatial magnitude, but
we must not admit that either the having the power to perceive or
the sense itself is a magnitude; what they are is a certain ratio or
power in a magnitude. This enables us to explain why objects of
sense which possess one of two opposite sensible qualities in a degree
largely in excess of the other opposite destroy the organs of sense;
if the movement set up by an object is too strong for the organ, the
equipoise of contrary qualities in the organ, which just is its
sensory power, is disturbed; it is precisely as concord and tone are
destroyed by too violently twanging the strings of a lyre. This
explains also why plants cannot perceive. in spite of their having a
portion of soul in them and obviously being affected by tangible
objects themselves; for undoubtedly their temperature can be lowered
or raised. The explanation is that they have no mean of contrary
qualities, and so no principle in them capable of taking on the
forms of sensible objects without their matter; in the case of
plants the affection is an affection by form-and-matter together.
The problem might be raised: Can what cannot smell be said to be
affected by smells or what cannot see by colours, and so on? It
might be said that a smell is just what can be smelt, and if it
produces any effect it can only be so as to make something smell it,
and it might be argued that what cannot smell cannot be affected by
smells and further that what can smell can be affected by it only in
so far as it has in it the power to smell (similarly with the proper
objects of all the other senses). Indeed that this is so is made quite
evident as follows. Light or darkness, sounds and smells leave
bodies quite unaffected; what does affect bodies is not these but
the bodies which are their vehicles, e.g. what splits the trunk of a
tree is not the sound of the thunder but the air which accompanies
thunder. Yes, but, it may be objected, bodies are affected by what
is tangible and by flavours. If not, by what are things that are
without soul affected, i.e. altered in quality? Must we not, then,
admit that the objects of the other senses also may affect them? Is
not the true account this, that all bodies are capable of being
affected by smells and sounds, but that some on being acted upon,
having no boundaries of their own, disintegrate, as in the instance of
air, which does become odorous, showing that some effect is produced
on it by what is odorous? But smelling is more than such an
affection by what is odorous-what more? Is not the answer that,
while the air owing to the momentary duration of the action upon it of
what is odorous does itself become perceptible to the sense of
smell, smelling is an observing of the result produced?
Book III
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1
THAT there is no sixth sense in addition to the five
enumerated-sight, hearing, smell, taste, touch-may be established by
the following considerations:
If we have actually sensation of everything of which touch can
give us sensation (for all the qualities of the tangible qua
tangible are perceived by us through touch); and if absence of a sense
necessarily involves absence of a sense-organ; and if (1) all
objects that we perceive by immediate contact with them are
perceptible by touch, which sense we actually possess, and (2) all
objects that we perceive through media, i.e. without immediate
contact, are perceptible by or through the simple elements, e.g. air
and water (and this is so arranged that (a) if more than one kind of
sensible object is perceivable through a single medium, the
possessor of a sense-organ homogeneous with that medium has the
power of perceiving both kinds of objects; for example, if the
sense-organ is made of air, and air is a medium both for sound and for
colour; and that (b) if more than one medium can transmit the same
kind of sensible objects, as e.g. water as well as air can transmit
colour, both being transparent, then the possessor of either alone
will be able to perceive the kind of objects transmissible through
both); and if of the simple elements two only, air and water, go to
form sense-organs (for the pupil is made of water, the organ of
hearing is made of air, and the organ of smell of one or other of
these two, while fire is found either in none or in all-warmth being
an essential condition of all sensibility-and earth either in none or,
if anywhere, specially mingled with the components of the organ of
touch; wherefore it would remain that there can be no sense-organ
formed of anything except water and air); and if these sense-organs
are actually found in certain animals;-then all the possible senses
are possessed by those animals that are not imperfect or mutilated
(for even the mole is observed to have eyes beneath its skin); so
that, if there is no fifth element and no property other than those
which belong to the four elements of our world, no sense can be
wanting to such animals.
Further, there cannot be a special sense-organ for the common
sensibles either, i.e. the objects which we perceive incidentally
through this or that special sense, e.g. movement, rest, figure,
magnitude, number, unity; for all these we perceive by movement,
e.g. magnitude by movement, and therefore also figure (for figure is a
species of magnitude), what is at rest by the absence of movement:
number is perceived by the negation of continuity, and by the
special sensibles; for each sense perceives one class of sensible
objects. So that it is clearly impossible that there should be a
special sense for any one of the common sensibles, e.g. movement; for,
if that were so, our perception of it would be exactly parallel to our
present perception of what is sweet by vision. That is so because we
have a sense for each of the two qualities, in virtue of which when
they happen to meet in one sensible object we are aware of both
contemporaneously. If it were not like this our perception of the
common qualities would always be incidental, i.e. as is the perception
of Cleon's son, where we perceive him not as Cleon's son but as white,
and the white thing which we really perceive happens to be Cleon's
son.
But in the case of the common sensibles there is already in us a
general sensibility which enables us to perceive them directly;
there is therefore no special sense required for their perception:
if there were, our perception of them would have been exactly like
what has been above described.
The senses perceive each other's special objects incidentally; not
because the percipient sense is this or that special sense, but
because all form a unity: this incidental perception takes place
whenever sense is directed at one and the same moment to two disparate
qualities in one and the same object, e.g. to the bitterness and the
yellowness of bile, the assertion of the identity of both cannot be
the act of either of the senses; hence the illusion of sense, e.g. the
belief that if a thing is yellow it is bile.
It might be asked why we have more senses than one. Is it to prevent
a failure to apprehend the common sensibles, e.g. movement, magnitude,
and number, which go along with the special sensibles? Had we no sense
but sight, and that sense no object but white, they would have
tended to escape our notice and everything would have merged for us
into an indistinguishable identity because of the concomitance of
colour and magnitude. As it is, the fact that the common sensibles are
given in the objects of more than one sense reveals their
distinction from each and all of the special sensibles.
2
Since it is through sense that we are aware that we are seeing or
hearing, it must be either by sight that we are aware of seeing, or by
some sense other than sight. But the sense that gives us this new
sensation must perceive both sight and its object, viz. colour: so
that either (1) there will be two senses both percipient of the same
sensible object, or (2) the sense must be percipient of itself.
Further, even if the sense which perceives sight were different from
sight, we must either fall into an infinite regress, or we must
somewhere assume a sense which is aware of itself. If so, we ought
to do this in the first case.
This presents a difficulty: if to perceive by sight is just to
see, and what is seen is colour (or the coloured), then if we are to
see that which sees, that which sees originally must be coloured. It
is clear therefore that 'to perceive by sight' has more than one
meaning; for even when we are not seeing, it is by sight that we
discriminate darkness from light, though not in the same way as we
distinguish one colour from another. Further, in a sense even that
which sees is coloured; for in each case the sense-organ is capable of
receiving the sensible object without its matter. That is why even
when the sensible objects are gone the sensings and imaginings
continue to exist in the sense-organs.
The activity of the sensible object and that of the percipient sense
is one and the same activity, and yet the distinction between their
being remains. Take as illustration actual sound and actual hearing: a
man may have hearing and yet not be hearing, and that which has a
sound is not always sounding. But when that which can hear is actively
hearing and which can sound is sounding, then the actual hearing and
the actual sound are merged in one (these one might call
respectively hearkening and sounding).
If it is true that the movement, both the acting and the being acted
upon, is to be found in that which is acted upon, both the sound and
the hearing so far as it is actual must be found in that which has the
faculty of hearing; for it is in the passive factor that the actuality
of the active or motive factor is realized; that is why that which
causes movement may be at rest. Now the actuality of that which can
sound is just sound or sounding, and the actuality of that which can
hear is hearing or hearkening; 'sound' and 'hearing' are both
ambiguous. The same account applies to the other senses and their
objects. For as the-acting-and-being-acted-upon is to be found in
the passive, not in the active factor, so also the actuality of the
sensible object and that of the sensitive subject are both realized in
the latter. But while in some cases each aspect of the total actuality
has a distinct name, e.g. sounding and hearkening, in some one or
other is nameless, e.g. the actuality of sight is called seeing, but
the actuality of colour has no name: the actuality of the faculty of
taste is called tasting, but the actuality of flavour has no name.
Since the actualities of the sensible object and of the sensitive
faculty are one actuality in spite of the difference between their
modes of being, actual hearing and actual sounding appear and
disappear from existence at one and the same moment, and so actual
savour and actual tasting, c., while as potentialities one of them
may exist without the other. The earlier students of nature were
mistaken in their view that without sight there was no white or black,
without taste no savour. This statement of theirs is partly true,
partly false: 'sense' and 'the sensible object' are ambiguous terms,
i.e. may denote either potentialities or actualities: the statement is
true of the latter, false of the former. This ambiguity they wholly
failed to notice.
If voice always implies a concord, and if the voice and the
hearing of it are in one sense one and the same, and if concord always
implies a ratio, hearing as well as what is heard must be a ratio.
That is why the excess of either the sharp or the flat destroys the
hearing. (So also in the case of savours excess destroys the sense
of taste, and in the case of colours excessive brightness or
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