Prior Analytics - Book II   

premisses. But an objection ought not to turn off into other things,

but have its new premiss quite clear immediately. For this reason also

this is the only figure from which proof by signs cannot be obtained.

We must consider later the other kinds of objection, namely the

objection from contraries, from similars, and from common opinion, and

inquire whether a particular objection cannot be elicited from the

first figure or a negative objection from the second.



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A probability and a sign are not identical, but a probability is a

generally approved proposition: what men know to happen or not to

happen, to be or not to be, for the most part thus and thus, is a

probability, e.g. 'the envious hate', 'the beloved show affection'.

A sign means a demonstrative proposition necessary or generally

approved: for anything such that when it is another thing is, or

when it has come into being the other has come into being before or

after, is a sign of the other's being or having come into being. Now

an enthymeme is a syllogism starting from probabilities or signs,

and a sign may be taken in three ways, corresponding to the position

of the middle term in the figures. For it may be taken as in the first

figure or the second or the third. For example the proof that a

woman is with child because she has milk is in the first figure: for

to have milk is the middle term. Let A represent to be with child, B

to have milk, C woman. The proof that wise men are good, since

Pittacus is good, comes through the last figure. Let A stand for good,

B for wise men, C for Pittacus. It is true then to affirm both A and B

of C: only men do not say the latter, because they know it, though

they state the former. The proof that a woman is with child because

she is pale is meant to come through the middle figure: for since

paleness follows women with child and is a concomitant of this

woman, people suppose it has been proved that she is with child. Let A