Kitap 2
25
When one of the company said to him, Convince me that logic is necessary,—Would you have me, he said, demonstrate it to you? Yes. Then I must use a demonstrative form of argument. Granted. And how will you know, then, whether I argue sophistically? On this, the man being silent, You see, says he, that even by your own confession, logic is necessary; since without it, you cannot even learn whether it be necessary or not.
What is the test of error.
26
Every error implies a contradiction; for since he who errs does not wish to err, but to be in the right, it is evident that he acts contrary to his wish. What does a thief desire to attain? His own interest. If, then, thieving be really against his interest, he acts contrary to his own desire. Now, every rational soul is naturally averse to self-contradiction; but so long as any one is ignorant that it is a contradiction, nothing restrains him from acting contradictorily; but whenever he discovers it, he must as necessarily renounce and avoid it, as any one must dissent from a falsehood whenever he perceives it to be a falsehood; only while this does not appear, he assents to it as to a truth.
