The first volume of the _Pyrrhonean Hypotyposes_ gives the most complete statement found in any of the works of Sextus Empiricus of the teachings of Pyrrhonism and its relation to other schools of philosophy. The chief source of the subject-matter presented is a work of the same name by Aenesidemus,[1] either directly used by Sextus, or through the writings of those who followed Aenesidemus. The comprehensive title [Greek: Purrhoneioi hupotuposeis] was very probably used in general to designate courses of lectures given by the leaders of the Sceptical School. In the opening chapters of the _Hypotyposes_ Sextus undertakes to define the position and aim of Pyrrhonism.[2] In introducing his subject he treats briefly of the differences between philosophical schools, dividing them into three classes; those which claim that they have found the truth, like the schools of Aristotle and Epicurus and the Stoics; those which deny the possibility of finding it, like that of the Academicians; and those that still seek it, like the Sceptical School. The accusation against the Academicians, that they denied the possibility of finding the truth, was one that the Sceptics were very fond of making. We shall discuss the justice of it later, simply remarking here, that to affirm the "incomprehensibility of the unknown," was a form of expression that the Pyrrhonists themselves were sometimes betrayed into, notwithstanding their careful avoidance of dogmatic statements.[3] [1] Diog. IX. 11, 78. [2] _Hyp._ I. 3, 4. [3] _Adv. Math._ VIII. 191. After defining the three kinds of philosophy as the Dogmatic, the Academic and the Sceptic, Sextus reminds his hearers that he does not speak dogmatically in anything that he says, but that he intends simply to present the Sceptical arguments historically, and as they appear to him. He characterizes his treatment of the subject as general rather than critical, including a statement of the character of Scepticism, its idea, its principles, its manner of reasoning, its criterion and aim, and a presentation of the Tropes, or aspects of doubt, and the Sceptical formulae and the distinction between Scepticism and the related schools of philosophy.[1] The result of all the gradual changes which the development of thought had brought about in the outward relations of the Sceptical School, was to increase the earnestness of the claim of the Sceptics to be simply followers of Pyrrho, the great founder of the movement. In discussing the names given to the Sceptics, Sextus gives precedence very decidedly to the title "Pyrrhonean," because Pyrrho appears the best representative of Scepticism, and more prominent than all who before him occupied themselves with it.[2]