Aristotle, Metaphysics Book Zeta (VII) Commentary ... - CATpages

Aristotle, Metaphysics, Zeta
species is called; if it were, that other would be
an element in 'man', i.e. would be the genus of
man. And further, (ii) all the elements of which
'man' is composed will be Ideas. None of them,
then, will be the Idea of one thing and the
substance of another; this is impossible. The
'animal', then, present in each species of animals
will be animal-itself. Further, from what is this
'animal' in each species derived, and how will it
be derived from animal-itself? Or how can this
'animal', whose essence is simply animality, exist
apart from animal-itself?
Further, (3) in the case of sensible things both
these consequences and others still more absurd
follow. If, then, these consequences are
impossible, clearly there are not Forms of
sensible things in the sense in which some
maintain their existence.
Chapter 15
Since substance is of two kinds, the concrete
thing and the formula (I mean that one kind of
substance is the formula taken with the matter,
while another kind is the formula in its
generality), substances in the former sense are
capable of destruction (for they are capable also
of generation), but there is no destruction of the
formula in the sense that it is ever in course of
being destroyed (for there is no generation of it
either; the being of house is not generated, but
only the being of this house), but without
generation and destruction formulae are and are
not; for it has been shown that no one begets nor
makes these. For this reason, also, there is
neither definition of nor demonstration about
sensible individual substances, because they have
matter whose nature is such that they are capable
both of being and of not being; for which reason
all the individual instances of them are
destructible. If then demonstration is of
necessary truths and definition is a scientific
process, and if, just as knowledge cannot be
sometimes knowledge and sometimes ignorance,
but the state which varies thus is opinion, so too
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