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

All this is true. The act of the agent is only connected with the effect, in
so far as it is moved, and the movement from potential to actual being is
what is called becoming. And, as Ghazali says, nonexistence is one of
the conditions for the existence of a movement through a mover.
Avicenna’s argument that when it is a condition for the act of the agent to
be connected with the existence, the absence of this connexion implies
that the agent is connected with its opposite, i.e. non-existence, is not
true. But the philosophers affirm that there are existents whose essential
specific differences consist in motion, e.g. the winds and so on; and the
heavens and the sublunary bodies belong to the genus of existents
whose existence lies in their movement, and if this is true, they are
eternally in a continual becoming. And therefore, just as the eternal
existent is more truly existent than the temporal, similarly that which is
eternally in becoming is more truly coming to be than that which comes to
be only during a definite time. And if the substance of the world were not
in this condition of continual movement, the world would not, after its
existence, need the Creator, just as a house after being completed and
finished does not need the builder’s existence, unless that were true
which Avicenna tried to prove in the preceding argument, that the
existence of the world consists only in its relation to the agent; and we
have already said that we agree with. him so far as this concerns the
forms of the heavenly bodies.
Therefore the world is during the time of its existence in need of the
presence of its agent for both reasons together, namely, because the
substance of the world is continually in motion and because its form,
through which it has its subsistence and existence, is of the nature of a
relation, not of the nature of a quality, i.e. the shapes and states which
have been enumerated in the chapter on quality. A form which belongs to
the class of quality, and is included in it, is, when it exists and its
existence is finished, in no need of an agent. All this will solve the
problem for you, and will remove from you the perplexity which befalls
man through these contradictory statements.’
Ghazali says, on behalf of the philosophers:
The philosophers might say: If you acknowledge that it is
possible that the act should be simultaneous with the agent
and not posterior to it, it follows that if the agent is temporal
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