both hear from admission and not from emission of something, and also taste, and similarly with the rest. Again, whatever are seen in all or in most things, we must take as principle and apparent theses, since persons lay down these who do not see, at the same time, in what thing it does not happen so. We must also select from written arguments, but descriptions must be made supposing separately about each genus; as about good or about animal, and about every good, beginning from what it is; we must also note besides, the several opinions, as that Empedocles said there are four elements of bodies, for any one would admit what had been asserted by some celebrated man.
But to speak comprehensively, there are three parts of propositions and of problems; for some propositions are ethical, others physical, but others logical. The ethical then are such, as whether it is right to obey parents rather than the laws, if the two are discordant; the logical, as whether there is the same science of contraries or not; and the physical, whether the world is perpetual or not; the like also occurs in problems. Still it is not easy to explain by definition, what the quality of each of the above-named is, but we must endeavour to know each of them from habit, which arises from induction, addressing our attention, according to the before-mentioned examples.
With regard then to philosophy, we must discuss these according to truth; but as to opinion, dialectically; still we must assume all the propositions as universal as possible, and make many one, as that there is the same science of opposites,
