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

would be no possibility of their avoiding the difficulty in this problem. But
you must understand that the philosophers permit the existence of a
temporal which comes out of a temporal being ad infinitum in an
accidental way, when this is repeated in a limited and finite matter-when,
for instance, the corruption of one of two things becomes the necessary
condition for the existence of the other. For instance, according to the
philosophers it is necessary that man should be produced from man on
condition that the anterior man perishes so as to become the matter for
the production of a third. For instance, we must imagine two men of whom
the first produces the second from the matter of a man who perishes;
when the second becomes a man himself, the first perishes, then the
second man produces a third man out of the matter of the first, and then
the second perishes and the third produces out of his matter a fourth, and
so we can imagine in two matters an activity continuing ad infinitum,
without any impossibility arising. And this happens as long as the agent
lasts, for if this agent has neither beginning nor end for his existence, the
activity has neither beginning nor end for its existence, as it has been
explained before. And in the same way you may imagine this happening in
them in the past: When a man exists, there must before him have been a
man who produced him and a man who perished, and before this second
man a man who produced him and a man who perished, for everything
that is produced in this way is, when it depends on an eternal agent, of a
circular nature in which no actual totality can be reached. If, on the other
hand, a man were produced from another man out of infinite matters, or
there were an infinite addition of them, there would be an impossibility, for
then there could arise an infinite matter and there could be an infinite
whole. For if a finite whole existed to which things were added ad infinitum
without any corruption taking place in it, an infinite whole could come into
existence, as Aristotle proved in his Physics. For this reason the ancients
introduce an eternal absolutely unchanging being, having in mind not
temporal beings, proceeding from him in so far as they are temporal, but
beings proceeding from him as being eternal generically, and they hold
that this infinite series is the necessary consequence of an eternal agent,
for the temporal needs for its own existence only a temporal cause. Now
there are two reasons why the ancients introduce the existence of an
eternal numerically unique being which does not suffer any change. The
first is that they discovered that this revolving being is eternal, for they
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