The Two Tropes.
Two other Tropes of ἐποχή are also taught. For as it appears that everything that is comprehended is either comprehended through itself or through something else, it is thought that this fact introduces doubt in regard to all things. And that nothing can be understood through itself is evident, it is said, from the disagreement which exists altogether among the physicists in regard to sensible and intellectual things. I mean, of course, a disagreement which cannot be judged, as we are not able to use a sensible or an intellectual criterion in judging it, for everything that we would take has a part in the disagreement, and is untrustworthy. Nor is it conceded that anything can be comprehended through something else; for if a thing is comprehended through something, that must always in turn be comprehended through something else, and the regressus in infinitum or the circulus in probando follow. If, on the contrary, a thing is comprehended through something that one wishes to use as if it had been comprehended through itself, this is opposed to the fact that nothing can be comprehended through itself, according to what we have said. We do not know how that which contradicts itself can be comprehended, either through itself or through something else, as no criterion of the truth or of comprehension appears, and signs without proof would be rejected, as we shall see in the next book. So much will suffice for the present about suspension of judgment.
CHAPTER XVII.
What are the Tropes for the overturning of Aetiology?
In the same manner as we teach the Tropes of ἐποχή, some set forth Tropes through which we oppose the Dogmatics, by expressing doubt in regard to the aetiology of which they are especially proud. So Aenesidemus teaches eight Tropes, by which he thinks that he can prove all the dogmatic aetiology useless. The first of these Tropes, he said, relates to the character of aetiology in general, which does not give incontestable testimony in regard to phenomena, because it treats of unseen things. The second Trope states that although abundant resources exist by which to investigate the cause of a thing in question, some Dogmatics investigate it in one way only. The third Trope states that the Dogmatics assign causes which do not show any order for things which have taken place in an orderly manner. The fourth Trope states that the Dogmatics, accepting phenomena as they take place, think that they also understand how unseen things take place, although perhaps the unseen things have taken place in the same way as the phenomena, and perhaps in some other way peculiar to themselves. The fifth Trope states that they all, so to speak, assign causes according to their own hypotheses about the elements, but not according to any commonly accepted methods. The sixth states that they often explain things investigated according to their own hypotheses, but ignore opposing hypotheses which have equal probability. The seventh states that they often give reasons for things that not only conflict with phenomena, but also with their own hypotheses. The eighth states that although that which seems manifest, and that which is to be investigated, are often equally inscrutable, they build up a theory from the one about the other, although both are equally inscrutable. It is not impossible, Aenesidemus said also, that some Dogmatics should fail in their theories of causality from other combinations of reasons deducible from the Tropes given above. Perhaps also the five Tropes of ἐποχή are sufficient to refute aetiology, for he who proposes a cause will propose one which is either in harmony with all the sects of philosophy, with Scepticism, and with phenomena, or one that is not. Perhaps, however, it is not possible that a cause should be in harmony with them, for phenomena and unknown things altogether disagree with each other. If it is not in harmony with them, the reason of this will also be demanded of the one who proposed it; and if he accepts a phenomenon as the cause of a phenomenon, or something unknown as the cause of the unknown, he will be thrown into the regressus in infinitum; if he uses one cause to account for another one, into the circulus in probando; but if he stops anywhere, he will either say that the cause that he proposes holds good so far as regards the things that have been said, and introduce relation, abolishing an absolute standpoint; or if he accepts anything by hypothesis, he will be attacked by us. Therefore it is perhaps possible to put the temerity of the Dogmatics to shame in aetiology by these Tropes.
CHAPTER XVIII.
The Sceptical Formulae.
When we use any one of these Tropes, or the Tropes of ἐποχή, we employ with them certain formulae which show the Sceptical method and our own feeling, as for instance, the sayings, "No more," "One must determine nothing," and certain others. It is fitting therefore to treat of these in this place. Let us begin with "No more."