in infinitum, it will have need of the intellectual, just as the intellectual has need of the sensible.  But he who accepts anything which is hypothetical again is absurd.  Intellectual things stand also 177 in relation, because the form in which they are expressed depends on the mind of the thinker, and, if they were in reality exactly as they are described, there would not have been any difference of opinion about them.  Therefore the intellectual also is brought under the five Tropes, and consequently it is necessary to suspend the judgment altogether with regard to every thing that is brought before us.  Such are the five Tropes taught by the later Sceptics.  They set them forth, not to throw out the ten Tropes, but in order to put to shame the audacity of the Dogmatics in a variety of ways, by these Tropes as well as by those.

CHAPTER XVI.

The Two Tropes.

Two other Tropes of [Greek:  epoche] are also taught.  For as it 178 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 179 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?