abricius, Cap. IV. H.

[7] Diog. III. 86.

[8] Pappenheim _Gr. Pyrr. Grundzuege_, p. 50.

[9] _Hyp._ I. 163.

[10] Diog. IX. 11, 83.

Following the exposition of the ten Tropes of the older
Sceptics, Sextus gives the five Tropes which he attributes to
the "later Sceptics."[1] Sextus nowhere mentions the author of
these Tropes. Diogenes, however, attributes them to Agrippa, a
man of whom we know nothing except his mention of him. He was
evidently one of the followers of Aenesidemus, and a scholar of
influence in the Sceptical School, who must have himself had
disciples, as Diogenes says, [Greek: hoi peri Agrippan][2] add
to these tropes other five tropes, using the plural verb.
Another Sceptic, also mentioned by Diogenes, and a man unknown
from other sources, named some of his books after Agrippa.[3]
Agrippa is not given by Diogenes in the list of the leaders of
the Sceptical School, but[4] his influence in the development of
the thought of the School must have been great, as the
transition from the ten Tropes of the "older Sceptics" to the
five attributed to Agrippa is a marked one, and shows the
entrance into the school of a logical power before unknown in
it. The latter are not a reduction of the Tropes of Aenesidemus,
but are written from an entirely different standpoint. The ten
Tropes are empirical, and aim to furnish objective proofs of the
foundation theories of Pyrrhonism, while the five are rather
rules of thought leading to logical proof, and are dialectic in
their character. We find this distinction illustrated by the
different way in which the Trope of relativity is treated in the
two groups. In the first it points to an objective relativity,
but with Agrippa to a general subjective logical principle. The
originality of the Tropes of Agrippa does not lie in their
substance matter, but in their formulation and use in the
Sceptical School. These methods of proof were, of course, not
new, but were well known to Aristotle, and were used by the
Sceptical Academy, and probably also by Timon,[5] while the
[Greek: pros ti] goes back at least to Protagoras. The five
Tropes are as follows.

(i) The one based upon discord.
(ii) The _regressus in infinitum_.
(iii) Relation.
(iv) The hypothetical.
(v) The _circulus in probando_.

Two of these are taken from the old list, the first and the
third, and Sextus says that the five Tropes are intended to
supplement the ten Tropes, and to sho