The Dogmatic, Academic, and Skeptic
Aenesidemus (1st century BCE) broke from the Academy and founded new school named after Pyrrho (who pursued a skeptical way of life but wrote nothing and established no school).
Sextus Empiricus (2nd or 3rd century CE)
"[It is called] 'Pyrrhonean (Πυρρώνειος)' from the fact that Pyrrho appears to us to have applied himself to Scepticism more thoroughly and more conspicuously than his predecessors" (Outlines of Pyrrhonism I.1.7).
Sextus Empiricus' Outlines of Pyrrhonism is the primary source for Pyrrhonian Skepticism.
"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 (ἀκαταληψίας) 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,' especially so called—Aristotle, for example, and Epicurus and the Stoics and certain others; Cleitomachus and Carneades and other Academics 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. ... [O]ur task at present is to describe in outline the Sceptic doctrine, 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" (Outlines of Pyrrhonism I.1.1-4).
"He, then, who suspends judgement about all things which depend on belief wins happiness most fully.... [This, however, does not mean that] he is confined to a state of inactivity.... [I]n arguing thus they do not comprehend that the Sceptic does not conduct his life according to philosophical theory (τὸν φιλόσοφον λόγον) (for so far as regards this he is inactive), but as regards the non-philosophic (τὴν ἀφιλόσοφον) regulation of life he is capable of desiring some things and avoiding others" (Sextus Empiricus, Against the Ethicists 160). "The originating cause of Scepticism is, we say, the hope of attaining quietude. Men of talent, who were perturbed by the contradictions in things and in doubt as to which of the alternatives they ought to accept, were led on to inquire what is true in things and what false, hoping by the settlement of this question to attain quietude. The main basic principle of the Sceptic system is that of opposing to every proposition an equal proposition; for we believe that as a consequence of this we end by ceasing to dogmatize" (Outlines of Pyrrhonism I.1.12).
"When we say that the Sceptic refrains from dogmatizing we do not use the term 'dogma (δόγμα),' as some do, in the broader sense of 'approval of a thing (εὐδοκεῖν)' (for the Sceptic gives assent to the feelings which are the necessary results of sense-impressions, and he would not, for example, say when feeling hot or cold 'I believe that I am not hot or cold'); but we say that 'he does not dogmatize' using 'dogma' in the sense, which some give it, of 'assent to one of the non-evident objects of scientific inquiry (τινι πράγματι τῶν κατὰ τὰς ἐπιστήμας ζητουμένων ἀδήλων συγκατάθεσιν)'; for the Pyrrhonean philosopher assents to nothing that is non-evident. Moreover, even in the act of enunciating the Sceptic formulae concerning things non-evident—such as the formula 'No more (one thing than another),' or the formula 'I determine nothing,' or any of the others which we shall presently mention,—he does not dogmatize. ... in his enunciation of these formulae he states what appears to himself and announces his own impression in an undogmatic way, without making any positive assertion regarding the external realities" (Outlines of Pyrrhonism I.1.13-15).
For example, honey appears to us to be sweet (and this we grant, for we perceive sweetness through the senses), but whether it is also sweet in its essence is for us a matter of doubt, since this is not an appearance but a judgement regarding the appearance (οἷον φαίνεται ἡμῖν γλυκάζειν τὸ μέλι. τοῦτο συγχωροῦμεν· γλυκαζόμεθα γὰρ αἰσθητικῶς. εἰ δὲ καὶ γλυκύ ἐστιν ὅσον ἐπὶ τῷ λόγῳ, ζητοῦμεν· ὃ οὐκ ἔστι τὸ φαινόμενον ἀλλὰ περὶ τοῦ φαινομένου λεγόμενον). And even if we do actually argue against the appearances, we do not propound such arguments with the intention of abolishing appearances, but by way of pointing out the rashness of the Dogmatists; for if reason (λόγος) is such a trickster as to all but snatch away the appearances from under our very eyes, surely we should view it with suspicion in the case of things non-evident so as not to display rashness by following it" (Outlines of Pyrrhonism I.1.19-20)
"Adhering, then, to appearances we live in accordance with the normal rules of life, undogmatically (ἀδοξάστως), seeing that we cannot remain wholly inactive. And it would seem that this regulation of life is fourfold, and that one part of it lies in the guidance of Nature, another in the constraint of the passions, another in the tradition of laws and customs, another in the instruction of the arts. Nature’s guidance is that by which we are naturally capable of sensation and thought (αἰσθητικοὶ καὶ νοητικοί); constraint of the passions is that whereby hunger drives us to food and thirst to drink; tradition of customs and laws, that whereby we regard piety in the conduct of life as good, but impiety as evil; instruction of the arts, that whereby we are not inactive in such arts as we adopt. But we make all these statements undogmatically" (Outlines of Pyrrhonism I.1.23-24).
"We assert still that the Sceptic's End is quietude in respect of matters of opinion and moderate feeling in respect of things unavoidable. For the Sceptic, having set out to philosophize with the object of passing judgement on the sense-impressions and ascertaining which of them are true and which false, so as to attain quietude thereby, found himself involved in contradictions of equal weight, and being unable to decide between them suspended judgement; and as he was thus in suspense there followed, as it happened, the state of quietude in respect of matters of opinion. For the man who opines that anything is by nature good or bad is for ever being disquieted: when he is without the things which he deems good he believes himself to be tormented by things naturally bad and he pursues after the things which are, as he thinks, good; which when he has obtained he keeps falling into still more perturbations because of his irrational and immoderate elation, and in his dread of a change of fortune he uses every endeavour to avoid losing the things which he deems good. On the other hand, the man who determines nothing as to what is naturally good or bad neither shuns nor pursues anything eagerly; and, in consequence, he is unperturbed" (Outlines of Pyrrhonism I.1.25-28).
"[T]he Sceptics were in hopes of gaining quietude by means of a decision regarding the disparity of the objects of sense and of thought, and being unable to effect this they suspended judgement; and they found that quietude, as if by chance, followed upon their suspense, even as a shadow follows its substance. We do not, however, suppose that the Sceptic is wholly untroubled; but we say that he is troubled by things unavoidable; for we grant that he is cold at times and thirsty, and suffers various affections of that kind. But even in these cases, whereas ordinary people are afflicted by two circumstances,—namely, by the affections themselves and, in no less a degree, by the belief that these conditions are evil by nature,—the Sceptic, by his rejection of the added belief in the natural badness of all these conditions, escapes here too with less discomfort. Hence we say that, while in regard to matters of opinion the Sceptic’s End is quietude, in regard to things unavoidable it is 'moderate affection'" (Outlines of Pyrrhonism I.1.29-30).
"About external existing things, we hold they are equal as far as this is a matter of reason (ἐπέχομεν ὅσον ἐπὶ τῷ λόγῳ)" Outlines of Pyrrhonism I.1.215).
“And as regards impressions, we say that they are equal in respect of probability and improbability, so far as this is a matter of reason (ἐπὶ τῷ λόγῳ), whereas they [adherents of the New Academy] assert that some impressions are probable, others improbable” (Outlines of Pyrrhonism I.1.227).
"[A]lthough both the Academics and the Sceptics say that they believe some things, yet here too the difference between the two philosophies is quite plain. For the word 'believe' (πείθεσθαι) has different meanings: it means not to resist but simply to follow without any strong impulse or inclination, as the boy is said to believe his tutor; but sometimes it means to assent to a thing of deliberate choice and with a kind of sympathy due to strong desire, as when the incontinent man believes him who approves of an extravagant mode of life. Since, therefore, Carneades and Cleitomachus declare that a strong inclination accompanies their credence and the credibility of the object, while we say that our belief is a matter of simple yielding without any consent (ἁπλῶς εἴκειν ἄνευ προσπαθείας)..." (Outlines of Pyrrhonism I.1.229-230).