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

I say
The second proof is that the intellect decides that black
and white are possible before they exist.’ If this possibility
were related to the body in which they inhere, so that it might
be said that the meaning is that this body can be black and
white, then white would not be possible by itself and
possibility would be related only to the body. But we affirm,
as concerns the judgement about black in itself, as to
whether it is possible, necessary, or impossible, that we,
without doubt, will say that it is possible. And this shows that
the intellect in order to decide whether something is possible
need not admit an existing thing to which the possibility can
be related.
This is a sophism. For the possible is predicated of the recipient and of
the inherent quality. In so far as it is predicated of the substratum, its
opposite is the impossible, and in so far as it is predicated of the inherent,
its opposite is the necessary.’ Thus the possible which is described as
being the opposite of the impossible is not that which abandons its
possibility so far as it is actualized, when it becomes actual, because this
latter loses its possibility in the actualizing process.’ This latter possible is
only described by possibility in so far as it is in potency, and the vehicle of
this potency is the substratum which changes from existence in potency
into existence in actuality.’ This is evident from the definition of the
possible that it is the nonexistence which is in readiness to exist or not to
exists This possible non-existent is possible neither in so far as it is nonexistent
nor in so far as it is actually existent. It is only possible in so far as
it is in potency, and for this reason the Mu’tazilites affirm that the
nonexistent is a kind of entity. For non-existence is the opposite of
existence, and each of the two is succeeded by the other, and when the
non-existence of a thing disappears it is followed by its existence, and
when its existence disappears it is succeeded by its non-existence. As
non-existence by itself cannot change into existence, and existence
by itself cannot change into non-existence, there must be a third entity
which is the recipient for both of them, and that is what is described by
‘possibility’ and ‘becoming’ and ‘change from the quality of non-existence
to the quality of existence’. For non-existence itself is not described by
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