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

For he says that the act of the agent must be connected either with an
existence or with a non-existence, previous to it and in so far as it is nonexistence,
or with both together, and that it is impossible that it should be
connected with non-existence, for the agent does not bring about nonexistence
and, therefore, neither can it effect both together. Therefore the
agent can be only connected with existence, and production is nothing but
the connexion of act with existence, i.e. the act of the agent is only
bringing into existence,’ and it is immaterial whether this existence be
preceded by non-existence or not. But this argument is faulty, because the
act of the agent is only connected with existence in a state of nonexistence,
i.e. existence in potentiality, and is not connected with actual
existence, in so far as it is actual, nor with non-existence, in so far as it is
non-existent. It is only connected with imperfect existence in which nonexistence
inheres. The act of the agent is not connected with nonexistence,
because non-existence is not actual; nor is it connected with
existence which is not linked together with non-existence, for whatever
has reached its extreme perfection of existence needs neither causation
nor cause. But existence which is linked up with non-existence only exists
as long as the producer exists. The only way to escape this difficulty is to
assume that the existence of the world has always been and will always
be linked together with non-existence, as is the case with movement,
which is always in need of a mover. And the acknowledged philosophers
believe that such is the case with the celestial world in its relation to the
Creator, and a fortiori with the sublunary world. Here lies the difference
between the created and the artificial, for the artificial product, once
produced, is not tied up with non-existence which would be in need of an
agent for the continued sustenance of the product.’
Ghazali continues:
And your statement, theologians, that what exists cannot
be made to exist, if you mean by it, that its existence does
not begin after its nonexistence, is true; but if you mean that
it cannot become an effect at the time when it exists, we
have shown that it can only become an effect at the time
when it exists, not at the time when it does not exist. For a
thing only exists when its agent causes it to exist, and the
agent only causes it to exist at the time when, proceeding
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