Quick wit is a faculty of hitting upon the middle term instantaneously. It would be exemplified by a man who saw that the moon has her bright side always turned towards the sun, and quickly grasped the cause of this, namely that she borrows her light from him; or observed somebody in conversation with a man of wealth and divined that he was borrowing money, or that the friendship of these people sprang from a common enmity. In all these instances he has seen the major and minor terms and then grasped the causes, the middle terms.
Let A represent 'bright side turned sunward', B 'lighted from the sun', C the moon. Then B, 'lighted from the sun' is predicable of C, the moon, and A, 'having her bright side towards the source of her light', is predicable of B. So A is predicable of C through B.
