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

I say:
necessary, not possible. But the necessary needs no cause.
So say, then, as the materialists do that you deny the creator
and that you deny the cause of causes! But this is not your
doctrine.
To this the answer which, Avicenna gives in accordance with his
doctrine is quite appropriate.’ According to him necessity of existence is of
two kinds: the necessary, existent by itself, and the necessary, existent
through another. But my answer on this question is still more to the point:
things necessary in this sense need not have an agent or a maker; take,
for example, a saw which is used to saw wood-it is a tool having a certain
determined quantity, quality, and matter, that is, it is not possible for it to
be of another material than iron and it could not have any other shape
than that of a saw or any other measure than the measure of a saw. Still
nobody would say that the saw has a necessity of being= See, therefore,
how crude this mistake is! If one were to take away the necessity from the
quantities, qualities, and matters of things produced by art, in the way the
Ash’arites imagine this to happen concerning the created in relation to the
creator, the wisdom which lies in the creator and the created would have
been withdrawn, any agent could be an artificer and any cause in
existence a creator. But all this is a denial of reason and wisdom.
Ghazali says:
The third reason is that this faulty argument authorizes its
opponent to oppose it by a similar one, and we may say: The
existence of the world was not possible before its existence,
for indeed possibility-according to your theory-is coextensive
with existence, neither more nor less. If you say: ‘But then
the eternal has passed from impotence to power’, we
answer:
‘No, for the existence was not possible and therefore
could not be brought about and the impossibility of a thing’s
happening that could not happen does not indicate
impotence.’ If you say: ‘How can a thing which is impossible
become possible?’ We answer: ‘But why should it be
impossible that a thing should be impossible at one moment
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