Posterior Analytics (Bouchier)/Book I/Chapter XXXIV

Chapter XXXIV: On Sagacity

 * Sagacity is a rapid perception of the middle term, or cause, resulting from a consideration of the major and minor terms.

Sagacity is a faculty for hitting upon the middle term in an imperceptible moment of time. For instance, suppose some one, seeing that the moon always has its bright side turned towards the sun, quickly inferred that this was so because the moon receives its light from the sun; or again, seeing someone conversing with a rich man, inferred that he was doing so in order to borrow money; or again inferred that the reason why two persons were friends of one another was that both were enemies of a third person. On seeing the major and minor of the syllogism the sagacious man is able to perceive all the causes or middle terms. Thus: Let A represent ‘having its bright side towards the sun’; B ‘lighted from the sun;’ C ‘the moon.’ Now B, ‘lighted from the sun,’ is true of C, the moon; A, ‘having their bright side towards the body from which the light is received’ is true of all objects denoted by B. Hence A is true of C because it is true of B.