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require as their subject the body of an animal; white and black

require a body, without further qualification; justice and injustice

require as their subject the human soul.

Moreover, it is necessary that pairs of contraries should in all

cases either belong to the same genus or belong to contrary genera

or be themselves genera. White and black belong to the same genus,

colour; justice and injustice, to contrary genera, virtue and vice;

while good and evil do not belong to genera, but are themselves actual

genera, with terms under them.






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There are four senses in which one thing can be said to be 'prior'

to another. Primarily and most properly the term has reference to

time: in this sense the word is used to indicate that one thing is

older or more ancient than another, for the expressions 'older' and

'more ancient' imply greater length of time.

Secondly, one thing is said to be 'prior' to another when the

sequence of their being cannot be reversed. In this sense 'one' is

'prior' to 'two'. For if 'two' exists, it follows directly that

'one' must exist, but if 'one' exists, it does not follow

necessarily that 'two' exists: thus the sequence subsisting cannot

be reversed. It is agreed, then, that when the sequence of two

things cannot be reversed, then that one on which the other depends is

called 'prior' to that other.

In the third place, the term 'prior' is used with reference to any

order, as in the case of science and of oratory. For in sciences which

use demonstration there is that which is prior and that which is

posterior in order; in geometry, the elements are prior to the

propositions; in reading and writing, the letters of the alphabet

are prior to the syllables. Similarly, in the case of speeches, the