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

I say:
And we say moreover to the philosophers: According to
your principles it is not absurd that there should be actual
units, qualitatively differentiated, which are infinite in number;
I am thinking of human souls, separated through death from
their bodies. These are therefore realities that can neither be
called even nor uneven. How will you refute the man who
affirms that this is necessarily absurd in the same way as
you claim the connexion between an eternal will and a
temporal creation to be necessarily absurd? This theory
about souls is that which Avicenna accented. and it is
perhaps Aristotle’s.
This argument is extremely weak. It says, in brief, ‘You philosophers
need not refute our assertion that what is a logical necessity for you is not
necessary, as you consider things possible which your adversaries
consider impossible by the necessity of thought. That is to say, just as you
consider things possible which your adversaries consider impossible, so
you consider things necessary which your adversaries do not consider so.
And you cannot bring a criterion for judging the two claims.’ It has already
been shown in the science of logic that this is a weak rhetorical or
sophistical kind of argument., The answer is that what we claim to be
necessarily true is objectively true, whereas what you claim as necessarily
absurd is not as you claim it to be. For this there is no other criterion than
immediate intuitive apprehension, just as, when one man claims that a line
is rhythmical and another denies it, the criterion is the intuition of the
sound understanding.
As for the thesis of a numerical plurality of immaterial souls, this is not a
theory acknowledged by the philosophers, for they regard matter as the
cause of numerical plurality and form as the cause of congruity in
numerical plurality. And that there should be a numerical plurality without
matter, having one unique form, is impossible. For in its description one
individual can only be distinguished from another accidentally, as there is
often another individual who participates in this descriptions but only
through their matter do individuals differ in reality. And also this: the
impossibility of an actual infinite is an acknowledged axiom in
philosophical theory, equally valid for material and immaterial things. We
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