(This is usually referred to by the abbreviation PH.)  Works of Classical literature were normally divided into ‘books’ (Plato’s Republic is in ten books, Aristotle’s Physics is in eight, etc.); PH is in three books. They are not given separate titles by scholars, and are just referred to as PH I, II, and III. PH I is a complete description of Pyrrhonian Skepticism, stating what it is that makes one qualify as a Pyrrhonian skeptic (the possession of a certain skill) and what the pay-off for being a Skeptic is (tranquillity), detailing the various ‘Modes’ of argumentation that the Skeptic deploys (mastery of which constitutes the skill which defines the skeptic) and the various phrases the Skeptic uses to indicate his characteristic state of mind, namely epochê or ‘suspension of judgment’, and differentiating Pyrrhonian Skepticism from other philosophical schools with which it might seem to have affinities. In PH II and III, Sextus lays out the positions of Dogmatic philosophers on issues of logic (PH II), and physics and ethics (PH III), complete with Skeptical counterarguments to those positions: essentially, we see Sextus in PH II and III exercising the Skeptical skill which he had described in PH I. (With Sextus’ description of Pyrrhonian Skepticism, compare that in DL (Diogenes Laërtius) IX 61–116; for discussion of the differences, see the papers in Vogt 2015.) 