Chapter XXV Parts of Philosophy
1. The first and most necessary point in philosophy is the use of the precepts, for example, not to lie. The second is the proof of these, as, Whence it comes that it is wrong to lie? The third is that which giveth confirmation and coherence to the others, such as, Whence it comes that this is proof? for what is proof? what is consequence? what is contradiction? what is truth? what is falsehood?
2. Thus the third point is necessary through the second, and the second through the first. But the most necessary of all, and that when we should rest, is the first, But we do the contrary. For we linger on the third point, and spend all our zeal on that, while of the first we are utterly neglectful, and thus we are liars; but the explanation of how it is shown to be wrong to lie we have ever ready to hand.