The natural result of any investigation is that the investigators either discover the object of search or deny that it is discoverable and confess it to be inapprehensible or persist in their search.

So, too, with regard to the objects investigated by philosophy, this is probably why some have claimed to have discovered the truth, others have asserted that it cannot be apprehended, while others again go on inquiring.

Those who believe they have discovered it are the ‟Dogmatists,” specially so called—Aristotle, for example, and Epicurus and the Stoics and certain others; Cleitomachus and Carneades and other AcademicsSee Introd. pp. xxxii ff. treat it as inapprehensible: the Sceptics keep on searching.

Hence it seems reasonable to hold that the main types of philosophy are three—the Dogmatic, the Academic, and the Sceptic. Of the other systems it will best become others to speak: our task at present is to describe in outline the Sceptic doctrine, ‟Doctrine.” ‟School,” ‟system” or ‟way” are other possible renderings of ἀγωγή. ‟Procedure,” ‟way of thought,” ‟trend,” or ‟line of argument,” ‟leading” (ἄγων) up to a definite goal, is rather what it connotes. first premising that of none of our future statements do we positively affirm that the fact is exactly as we state it, but we simply record each fact, like a chronicler, as it appears to us at the moment.