stantial existence, and that which is neither substantial nor existent cannot have had the chance of coming into being either. There is nothing good or bad by nature, for if there is anything good or bad by nature, it must be good or bad for all persons alike, just as snow is cold to all. But there is no good or bad which is such to all persons in common ; therefore there is no such thing as good or bad by nature. For either all that is thought good by anyone whatever must be called good, or not all. Certainly all cannot be so called ; since one and the same thing is thought good by one person and bad by another ; for instance, Epicurus thought pleasure good and Antisthenes thought it bad ; thus on our supposition it will follow that the same thing is both good and bad. But if we say that not all that anyone thinks good is good, we shall have to judge the different opinions ; and this is impossible because of the equal validity of opposing arguments. Therefore the good by nature is unknowable. The whole of their mode of inference can be gathered from their extant treatises. Pyrrho himself, indeed, left no writings, but his associates Timon, Aenesidemus, Numenius and Nausiphanes did ; and others as well. The dogmatists answer them by declaring that the Sceptics themselves do apprehend and dogmatize for when they are thought to be refuting their hardest they do apprehend, for at the very same time they are asseverating and dogmatizing. Thus even when they declare that they determine nothing, and that to every argument there is an opposite argument, they are actually determining these very points and dogmatizing. The others reply, " We