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

I say:
If it is said: In the same way as the series of efficient
causes must have an end, the series of receptive causes
must have an end, since if every existent needed a
substratum to inhere in it and this substratum again needed
a substratum, this would imply an infinite series, just as this
would be the case if every existent needed a cause and this
cause again another causewe answer: You are perfectly
right and for this very reason we say that the series has an
end and that the attribute exists in its essence and that this
essence does not exist in something else, just as our
knowledge exists in our essence and our essence is its
substratum, but does not exist itself in a substratum.
This statement has no connexion with this discussion either with
respect to the philosophical theories he mentions or with respect to the
answers he gives, and it is a kind of sophism, for there exists no relation
between the question, whether the receptive causes must or must not
have an end, and the problem which is under discussion, namely whether
it is a condition of the First Agent that it should have a receptive cause.
For the inquiry about the finiteness of receptive causes differs from the
inquiry about the finiteness of efficient causes, since he who admits the
existence of receptive causes admits necessarily that their series must
end in a primary receptive cause which is necessarily external to the First
Agent, just as he admits the existence of a First Agent external to the
receptive matter. For if the First Agent possessed matter, this matter
would not exist numerically and individually either in the first recipient or in
the inferior recipients of other things; ‘ no, if the First Agent possessed
matter, this matter would have to be a matter peculiar to it, and in short it
would belong to it; that is, either it would be its primary matter or we
should arrive at a first recipient, and this recipient would not be of the
genus which is the condition for the existence of all the other existents
proceeding from the First Agent. ‘ But if matter were the condition for the
existence of the First Agent, it would be a condition for the existence of all
agents in their actions, and matter would not only be a condition for the
existence of the agent’s act-since every agent acts only on a recipient -but
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