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
demonstration and definition cannot vary thus, but it is opinion
that deals with that which can be otherwise than as it is, clearly
there can neither be definition of nor demonstration about sensible
individuals. For perishing things are obscure to those who have the
relevant knowledge, when they have passed from our perception; and
though the formulae remain in the soul unchanged, there will no longer
be either definition or demonstration. And so when one of the
definition-mongers defines any individual, he must recognize that
his definition may always be overthrown; for it is not possible to
define such things.
Nor is it possible to define any Idea. For the Idea is, as its
supporters say, an individual, and can exist apart; and the formula
must consist of words; and he who defines must not invent a word
(for it would be unknown), but the established words are common to all
the members of a class; these then must apply to something besides the
thing defined; e.g. if one were defining you, he would say 'an
animal which is lean' or 'pale', or something else which will apply
also to some one other than you.
Pages:
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207