[1039b]
[1]
how can the one which in things that exist
separately be one, and why should not this "animal" also be separated
from itself? Again, if it is to partake of "two-footed" and of
"many-footed," an impossibility follows; for contrary attributes will
belong to it although it is one and individual.But if it does not, in what sense is it
that one calls an animal "two-footed" or "terrestrial"? Perhaps the
terms are "combined" and "in contact" or "mixed." But all these
expressions are absurd.(2) "But there
is a different 'animal' in each species." Then there will be
practically an infinity of things of which "animal" is the substance,
since it is not in an accidental sense that "man" is derived from
"animal."Again, the
Absolute Animal will be a plurality. For (a) the "animal" in each
species will be the substance of that species, since the species is
called after it and no other thing. Otherwise "man" would be derived
from that other thing, which would be the genus of "man." (b) Further,
all the constituents of "man" will be Ideas. Then, since nothing can
be the Idea of one thing and the substance of another (for this is
impossible),each
and every "animal" in the various species will be the Absolute
Animal.Further, from what will
these Forms be derived, and how can they be derived from the Absolute
Animal? Or how can "the animal," whose very essence is "animal," exist
apart from the Absolute Animal? And further, in the case of sensible
things both these and still more absurd consequences follow. If, then,
these consequences are impossible, clearly there are not Forms of
sensible things in the sense in which some hold that there
are.
[20]
Since
substance is of two kinds, the concrete thing and the formula (I mean
that one kind of substance is the formula in combination with the
matter, and the other is the formula in its full sense), substances in
the former sense admit of destruction, for they also admit of
generation. But the formula does not admit of destruction in the sense
that it is ever being destroyed, since neither does it so
admit of generation (for the essence of house is not generated, but
only the essence of this house); formulae
are , and are not, independently of
generation and destruction; for it has been shown1 that no one either generates or
creates them.For this
reason also there is no definition or demonstration of particular
sensible substances, because they contain matter whose nature is such
that it can both exist and not exist. Hence all the individual
instances of them are perishable.If, then, the demonstration and definition of
necessary truths requires scientific knowledge, and if, just as
knowledge cannot be sometimes knowledge and sometimes ignorance (it is
opinion that is of this nature), so too demonstration and definition
cannot vary (it is opinion that is concerned with that which can be
otherwise than it is)—
1 Cf. Aristot. Met. 7.8.3.
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