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

becomes; what becomes is only the form, the accidents and
the qualities which add themselves to matters The proof is
that the existence of each thing that becomes must, before
its becoming, either be possible, impossible, or necessary: it
cannot be impossible, for the essentially impossible will
never exist; it cannot be necessary, for the essentially
necessary will never be in a state of non-existence, and
therefore it is the essentially possible.’ Therefore, the thing
which becomes has before its becoming the possibility of
becoming, but the possibility of becoming is an attribute
which needs a relation and has no subsistence in itself.’ It
needs, therefore, a substratum with which it can be
connected, and there is no substratum except matter, and it
becomes connected with it in the way in which we say this
matter receives warmth and coldness, or black and white, or
movement and rest, i.e. it is possible that these qualities and
these changes occur in it and therefore possibility is an
attribute of matter. Matter does not possess other matter,
and cannot become; for, if it did, the possibility of its
existence would precede its existence, and possibility would
subsist by itself without being related to anything else,
whereas it is a relative attribute which cannot be understood
as subsisting by itself. And it cannot be said that the
meaning of possibility amounts to what can be done and
what the Eternal had the power to do, because we know only
that a thing can be done, because it is possible, and we say
‘this can be done because it is possible and cannot be done
because it is not possible’; and if ‘this is possible’ meant ‘this
can be done’, to say ‘this can be done because it is possible’
would mean ‘this is possible because it is possible’, and this
is a circular definition; and this shows that ‘this is possible’ is
a first judgement in the mind, evident in itself, which makes
the second judgement ‘that it can be done’ intelligible. It
cannot be said, either, that to be possible refers to the
knowledge of the Eternal, for knowledge depends on a thing
known, whereas possibility is undoubtedly an object of
knowledge, not knowledge; further, it is a relative attribute,
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