Everything, we say, that undergoes alteration is altered by sensible
causes, and there is alteration only in things that are said to be
essentially affected by sensible things. The truth of this is to be
seen from the following considerations. Of all other things it would
be most natural to suppose that there is alteration in figures and
shapes, and in acquired states and in the processes of acquiring and
losing these: but as a matter of fact in neither of these two
classes of things is there alteration.

    In the first place, when a particular formation of a thing is
completed, we do not call it by the name of its material: e.g. we do
not call the statue "bronze" or the pyramid "wax" or the bed "wood",
but we use a derived expression and call them "of bronze", "waxen",
and "wooden" respectively. But when a thing has been affected and
altered in any way we still call it by the original name: thus we
speak of the bronze or the wax being dry or fluid or hard or hot.

    And not only so: we also speak of the particular fluid or hot
substance as being bronze, giving the material the same name as that
which we use to describe the affection.

    Since, therefore, having regard to the figure or shape of a thing we
no longer call that which has become of a certain figure by the name
of the material that exhibits the figure, whereas having regard to a
thing's affections or alterations we still call it by the name of
its material, it is evident that becomings of the former kind cannot
be alterations.

    Moreover it would seem absurd even to speak in this way, to speak,
that is to say, of a man or house or anything else that has come
into existence as having been altered. Though it may be true that
every such becoming is necessarily the result of something's being
altered, the result, e.g. of the material's being condensed or
rarefied or heated or cooled, nevertheless it is not the things that
are coming into existence that are altered, and their becoming is
not an alteration.

    Again, acquired states, whether of the body or of the soul, are
not alterations. For some are excellences and others are defects,
and neither excellence nor defect is an alteration: excellence is a
perfection (for when anything acquires its proper excellence we call
it perfect, since it is then if ever that we have a thing in its
natural state: e.g. we have a perfect circle when we have one as
good as possible), while defect is a perishing of or departure from
this condition. So as when speaking of a house we do not call its
arrival at perfection an alteration (for it would be absurd to suppose
that the coping or the tiling is an alteration or that in receiving
its coping or its tiling a house is altered and not perfected), the
same also holds good in the case of excellences and defects and of the
persons or things that possess or acquire them: for excellences are
perfections of a thing's nature and defects are departures from it:
consequently they are not alterations.

    Further, we say that all excellences depend upon particular
relations. Thus bodily excellences such as health and a good state
of body we regard as consisting in a blending of hot and cold elements
within the body in due proportion, in relation either to one another
or to the surrounding atmosphere: and in like manner we regard beauty,
strength, and all the other bodily excellences and defects. Each of
them exists in virtue of a particular relation and puts that which
possesses it in a good or bad condition with regard to its proper
affections, where by "proper" affections I mean those influences
that from the natural constitution of a thing tend to promote or
destroy its existence. Since then, relatives are neither themselves
alterations nor the subjects of alteration or of becoming or in fact
of any change whatever, it is evident that neither states nor the
processes of losing and acquiring states are alterations, though it
may be true that their becoming or perishing is necessarily, like
the becoming or perishing of a specific character or form, the
result of the alteration of certain other things, e.g. hot and cold or
dry and wet elements or the elements, whatever they may be, on which
the states primarily depend. For each several bodily defect or
excellence involves a relation with those things from which the
possessor of the defect or excellence is naturally subject to
alteration: thus excellence disposes its possessor to be unaffected by
these influences or to be affected by those of them that ought to be
admitted, while defect disposes its possessor to be affected by them
or to be unaffected by those of them that ought to be admitted.

    And the case is similar in regard to the states of the soul, all
of which (like those of body) exist in virtue of particular relations,
the excellences being perfections of nature and the defects departures
from it: moreover, excellence puts its possessor in good condition,
while defect puts its possessor in a bad condition, to meet his proper
affections. Consequently these cannot any more than the bodily
states be alterations, nor can the processes of losing and acquiring
them be so, though their becoming is necessarily the result of an
alteration of the sensitive part of the soul, and this is altered by
sensible objects: for all moral excellence is concerned with bodily
pleasures and pains, which again depend either upon acting or upon
remembering or upon anticipating. Now those that depend upon action
are determined by sense-perception, i.e. they are stimulated by
something sensible: and those that depend upon memory or
anticipation are likewise to be traced to sense-perception, for in
these cases pleasure is felt either in remembering what one has
experienced or in anticipating what one is going to experience. Thus
all pleasure of this kind must be produced by sensible things: and
since the presence in any one of moral defect or excellence involves
the presence in him of pleasure or pain (with which moral excellence
and defect are always concerned), and these pleasures and pains are
alterations of the sensitive part, it is evident that the loss and
acquisition of these states no less than the loss and acquisition of
the states of the body must be the result of the alteration of
something else. Consequently, though their becoming is accompanied
by an alteration, they are not themselves alterations.

    Again, the states of the intellectual part of the soul are not
alterations, nor is there any becoming of them. In the first place
it is much more true of the possession of knowledge that it depends
upon a particular relation. And further, it is evident that there is
no becoming of these states. For that which is potentially possessed
of knowledge becomes actually possessed of it not by being set in
motion at all itself but by reason of the presence of something
else: i.e. it is when it meets with the particular object that it
knows in a manner the particular through its knowledge of the
universal. (Again, there is no becoming of the actual use and activity
of these states, unless it is thought that there is a becoming of
vision and touching and that the activity in question is similar to
these.) And the original acquisition of knowledge is not a becoming or
an alteration: for the terms "knowing" and "understanding" imply
that the intellect has reached a state of rest and come to a
standstill, and there is no becoming that leads to a state of rest,
since, as we have said above, change at all can have a becoming.
Moreover, just as to say, when any one has passed from a state of
intoxication or sleep or disease to the contrary state, that he has
become possessed of knowledge again is incorrect in spite of the
fact that he was previously incapable of using his knowledge, so, too,
when any one originally acquires the state, it is incorrect to say
that he becomes possessed of knowledge: for the possession of
understanding and knowledge is produced by the soul's settling down
out of the restlessness natural to it. Hence, too, in learning and
in forming judgements on matters relating to their sense-perceptions
children are inferior to adults owing to the great amount of
restlessness and motion in their souls. Nature itself causes the
soul to settle down and come to a state of rest for the performance of
some of its functions, while for the performance of others other
things do so: but in either case the result is brought about through
the alteration of something in the body, as we see in the case of
the use and activity of the intellect arising from a man's becoming
sober or being awakened. It is evident, then, from the preceding
argument that alteration and being altered occur in sensible things
and in the sensitive part of the soul, and, except accidentally, in
nothing else.