Consequently also in reasoning what has been said is not enough; but is it necessary that a man should acquire the faculty of examining and distinguishing the true and the false, and that which is not plain? "It is necessary." Besides this, what is proposed in reasoning? "That you should accept what follows from that which you have properly granted." Well, is it then enough in this case also to know this? It is not enough; but a man must learn how one thing is a consequence of other things, and when one thing follows from one thing, and when it follows from several collectively. Consider, then if it be not necessary that this power should also be acquired by him who purposes to conduct himself skillfully in reasoning, the power of demonstrating himself the several things which he has proposed, and the power of understanding the demonstrations of others, including of not bein