_The Two Tropes._
Two other Tropes of [Greek: epochê] 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.