Tahafut_al-Tahafut-transl-Engl-van-den-Bergh

When it is conceded that the intellect is not related to one of man’s
organs-and this has already been proved, since it is not self-evident -it
follows that its substratum is not a body, and that our assertion that man
knows is not analogous to our assertion that he sees. For since it is selfevident
that he sees through a particular organ, it is clear that when we
refer sight to man absolutely, the expression is allowed according to the
custom of the Arabs and other people. ; And since there is no particular
organ for the intellect, it is clear that, when we say of him that he knows,
this does not mean that a part of him knows. However, how he knows is
not clear by itself, for it does not appear that there is an organ or a special
place in an organ which possesses this special faculty, as is the case with
the imaginative faculty and the cogitative and memorative faculties, the
localization of which in parts of the brain is known.
Ghazali says:
The fourth proof is that, if knowledge inhered for instance
in a part of the heart or the brain, then necessarily
ignorance, its opposite, might reside in another part of the
heart or the brain, and it would then be possible that a man
should both know and not know one and the same thing at
the same time. And since this is impossible, it is proved that
the place of ignorance and the place of knowledge are
identical, and that this place is one single place in which it is
impossible to bring opposites together. But if this place were
divisible, it would not be impossible that ignorance should
reside in one part of it and knowledge in another, for a
thing’s being in one place is not contradicted by its
opposite’s being in another, just as there may be pie
baldness in one and the same horse, and black and white in
a single eye, but in two spots. This, however, does not follow
for the senses, as there is no opposite to their perception;
but sometimes they perceive and sometimes not, and there
exists between them the sole opposition of being and notbeing,
and we can surely say that someone perceives
through some parts, for instance the eye and the ear, and
not through the other parts of his body; and there is no
contradiction in this. And you cannot evade this difficulty by
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