From Eusebius of Caesarea: Praeparatio Evangelica (Preparation for the Gospel). Translated by E.H. Gifford (1903), Book 14
Such then were the followers of Xenophanes, who is said to have flourished at the same time with Pythagoras and Anaxagoras. Now a hearer of Xenophanes was Parmenides, and of Parmenides Melissus, of him Zeno, of him Leucippus, of him Democritus, of him Protagoras and Nessas, and of Nessas Metrodorus, of him Diogenes, of him Anaxarchus, and a disciple of Anaxarchus was Pyrrho, from whom arose the school of those who were surnamed Sceptics. And as these also laid it down that no conception of anything was possible either by sense or by reason, but suspended their judgement in all cases, we may learn how they were refuted by those who held an opposite opinion, from the book before mentioned [Aristocles On Philosophy], speaking word for word as follows:
"Before all things it is necessary to make a thorough examination of our own knowledge; for if it is our nature to know nothing there is no further need to inquire about other things.
'Some then there were even of the ancients who spoke this language, and who have been opposed by Aristotle. Pyrrho indeed, of Elis, spoke strongly in this sense, but has not himself left anything in writing. But his disciple Timon says that the man who means to be happy must look to these three things: first, what are the natural qualities of things; secondly, in what way we should be disposed towards them; and lastly, what advantage there will be to those who are so disposed.
'The things themselves then, he professes to show, are equally indifferent, and unstable, and indeterminate, and therefore neither our senses nor our opinions are either true or false. For this reason then we must not trust them, but be without opinions, and without bias, and without wavering, saying of every single thing that it no more is than is not, or both is and is not, or neither is nor is not.
'To those indeed who are thus disposed the result, Timon says, will be first speechlessness, and then imperturbability, but Aenesidemus says pleasure.
'These then are the chief points of their arguments: and now let us consider whether they are right in what they say. Since therefore they say that all things are equally indifferent, and bid us for this reason attach ourselves to none, nor hold any opinion, I think one may reasonably ask them, whether those who think things differ are in error or not. For if they are in error, surely they cannot be right in their supposition. So they will be compelled to say that there are some who have false opinions about things, and they themselves therefore must be those who speak the truth: and so there must be truth and falsehood. But if we the many are not in error in thinking that things differ, what do they mean by rebuking us? For they must be in error themselves in maintaining that they do not differ.
'Moreover if we should even grant to them that all things are equally indifferent, it is evident that even they themselves would not differ from the multitude. What then would their wisdom, be? And why does Timon abuse all other persons, and sing the praises of Pyrrho only?
'Yet, further, if all things are equally indifferent and we ought therefore to have no opinion, there would be no difference even in these cases, I mean in the differing or not differing, and the having or not having an opinion. For why should things of this kind be rather than not be? Or, as Timon says, why "yes," and why "no," and why the very "Why?" itself? It is manifest therefore that inquiry is done away: so let them cease from troubling. For at present there is no method in their madness, while, in the very act of admonishing us to have no opinion, they at the same time bid us to form an opinion, and in saying that men ought to make no statement they make a statement themselves: and though they require you to agree with no one, they command you to believe themselves: and then though they say they know nothing, they reprove us all, as if they knew very well.
'And those who assert that all things are uncertain must do one of two things, either be silent, or speak and state something. If then they should hold their peace, it is evident that against such there would be no argument. But if they should make a statement, anyhow and by all means they must say that something either is or is not, just as they certainly now say that all things are to all men matters not of knowledge but of customary opinion, and that nothing can be known.
'The man therefore who maintains this either makes the matter clear, and it is possible to understand it as spoken, or it is impossible. But if he does not make it clear, there can be absolutely no arguing in this case either with such a man. But if he should make his meaning clear, he must certainly either state what is indefinite or what is definite: and if indefinite, neither in this case would there be any arguing with him, for of the indefinite there can be no knowledge. But if the statements, or any one of them whatever, be definite, the man who states this defines something and decides. How then can all things be unknowable and indeterminate? But should he say that the same thing both is and is not, in the first place the same thing will be both true and false, and next he will both say a thing and not say it, and by use of speech will destroy speech, and moreover, while acknowledging that he speaks falsely, says that we ought to believe him.
'Now it is worth inquiring whence they learned what they say, that all things are uncertain. For they ought to know beforehand what certainty is: thus at all events they would be able to say that things have not this quality of certainty. First they ought to know affirmation, and then negation. But if they are ignorant of the nature of certainty, neither can they know what uncertainty is.
'When indeed Aenesidemus in his Outline goes through the nine moods (in all of which he has attempted to prove the uncertainty of things), which are we to say, that he speaks with knowledge of them or without knowledge? For he says that there is a difference in animals, and in ourselves, and in states, and in the modes of life, and customs, and laws: he says also that our senses are feeble, and that the external hindrances to knwoledge are many, such as distances, magnitudes, and motions: and further, the difference of condition in men young and old, and waking and sleeping, and healthy and sick: and nothing that we perceive is simple and unmixed; for all things are confused, and spoken in a relative sense.
'But when he was making these and other such fine speeches, one would have liked, I say, to ask hirn whether he was stating with full knowledge that this is the condition of things, or without knowledge. For if he did not know, how could we believe him? But if he knew, he was vastly silly for declaring at the same time that all things are uncertain, and yet saying that he knew so much.
'Moreover whenever they go through such details, they are only making a sort of induction, showing what is the nature of the phenomena and of the particulars: and a process of this kind both is, and is called, a proof. If therefore they assent to it, it is evident that they form an opinion: and if they disbelieve it, neither should we choose to give heed to them.
'Timon moreover in the Python relates a story at great length, how he met Pyrrho walking towards Delphi past the temple of Amphiaraus, and what they talked about to each other. Might not then any one who stood beside him while writing this reasonably say, Why trouble yourself, poor fellow, in writing this, and relating what you do not know? For why rather did you meet him than not meet him, and talk with him rather than not talk?
'And this same wonderful Pyrrho, did he know the reason why he was walking to see the Pythian games? Or was he wandering, like a madman, along the road? And when he began to find fault with mankind and their ignorance, are we to say that he spoke truth or not, and that Timon was affected in a certain way and agreed with his sayings, or did not heed them? For if he was not persuaded, how did he pass from a choral dancer to a philosopher, and continue to be an admirer of Pyrrho? But if he agreed with what was said, he must be an absurd person for taking to philosophy himself but forbidding us to do so.
'And one must simply wonder what is the meaning to them of Timon's lampoons and railings against all men, and the tedious Rudiments of Aenesidemus and all the like multitude of words. For if they have written these with an idea that they would render us better, and therefore think it right to confute us all, that so we may cease to talk nonsense, it is evidently their wish that we should know the truth, and assume that things are such as Pyrrho maintains. So if we were to be persuaded by them we should change from worse to better, by forming the more advantageous judgements, and approving those who gave the better advice.
'How then could things possibly be equally indifferent and indeterminate? And how could we avoid giving assent and forming opinions? And if there is no use in arguments, why do they trouble us? Or why does Timon say,
No other mortal could with Pyrrho vie"?
For one would not admire Pyrrho any more than the notorious Coroebus or Meletides, who are thought to excel in stupidity.
'We ought, however, to take also the following matters into consideration. For what sort of citizen, or judge, or counsellor, or friend, or, in a word, what sort of man would such an one be? Or what evil deeds would not he dare, who held that nothing is really evil, or disgraceful, or just or unjust? For one could not say even this, that such men are afraid of the laws and their penalties; for how should they, seeing that, as they themselves say, they are incapable of feeling or of trouble?
'Timon indeed even says this of Pyrrho:
"O what a man I knew, void of conceit,
Daunted by none, who whether known to fame
Or nameless o'er the fickle nations rule,
This way and that weighed down by passion's force,
Opinion false, and legislation vain."
'When, however, they utter this wise saw, that one ought to live in accordance with nature and with customs, and yet not to assent to anything, they are too silly. For they require one to assent to this at least, if to nothing else, and to assume that it is so. But why ought one, rather than ought not, to follow nature and customs, if forsooth we know nothing, and have no means whereby to judge?
'It is altogether a silly thing, when they say, that just as cathartic drugs purge out themselves together with the excrements, in like manner the argument which maintains that all things are uncertain together with everything else destroys itself also. For supposing it to refute itself, they who use it must talk nonsense. It were better therefore for them to hold their peace, and not open their mouth at all,
'But in truth there is no similarity between the cathartic drug and their argument. For the drug is secreted and does not remain in the body: the argument, however, must be there in men's souls, as being always the same and gaining their belief, for it can be only this that makes them incapable of assent.
'But that it is not possible for a man to have no opinions, one may learn in the following manner. For it is impossible that he who perceives by sense does not perceive: now perception by sense is a kind of knowledge. And that he also believes his sensation is evident to all: for when he wishes to see more exactly, he wipes his eyes, and comes nearer, and shades them.
'Moreover we know that we feel pleasure and pain: for it is not possible for one who is being burned or cut to be ignorant of it. And who would not say that acts of memory surely and of recollection are accompanied by an assumption? But what need one say about common concepts, that such a thing is a man, and again concerning sciences and arts? For there would be none of these, were it not our nature to make assumptions. But for my part I pass over all other arguments. Whether, however, we believe, or whether we disbelieve the arguments used by them, in every way it is an absolute necessity to form an opinion.
'It is manifest then that it is impossible to study philosophy in this fashion; and that it is also unnatural and contrary to the laws, we may perceive as follows. For if on the other hand things were in reality of this kind, what would remain but that we must live as if asleep, in a random and senseless fashion? So that our lawgivers, and generals, and educators must all be talking nonsense. To me, however, it seems that all the rest of mankind are living in a natural way, but only those who talk this nonsense are puffed up with conceit, or rather are gone stark mad.
'Not least, however, one may learn this from the following case. Antigonus, for instance, of Carystus, who lived about the same times and wrote their biography, says that Pyrrho being pursued by a dog escaped up a tree, and, when laughed at by those who stood by, said that it was difficult to put off the man. And when his sister Philiste was to offer a sacrifice, and then one of her friends promised what was necessary for the sacrifice and did not provide it, but Pyrrho bought it, and was angry, upon his friend saying that his acts were not in accord with his words nor worthy of his impassivity, he replied, In the case of a woman certainly we ought not to make proof of it. Nevertheless his friend might fairly have answered, If there is any good in these arguments of yours, your impassivity is useless in the case even of a woman, or a dog, and in all cases.
'But it is right to ascertain both who they were that admired him, and whom he himself admired. Pyrrho then was a disciple of one Anaxarchus, and was at first a painter, and not very successful at that; next, after reading the books of Democritus, he neither found anything useful there nor wrote anything good himself, but spake evil of all, both gods and men. But afterwards wrapping himself up in this conceit, and calling himself free from conceit, he left nothing in writing.
'A disciple of his was Timon of Phlius, who at first was a dancer in the chorus at the theatres, but having afterwards fallen in with Pyrrho he composed offensive and vulgar parodies, in which he has reviled all who ever studied philosophy. For this was the man who wrote the Silli, and said:
"Mankind how poor and base, born but to eat,
Your life made up of shame, and strife, and woe."
And again:
"Men are but bags with vain opinions filled."
'When nobody took notice of them any more than if they had never been born, a certain Aenesidemus began just yesterday to stir up this nonsense again at Alexandria in Egypt. And these are just the men who were thought to be the mightiest of those who had trodden this path.
'It is evident then that no one in his right mind would approve such a sect, or course of argument, or whatever and however any one likes to call it. For I think for my part that we ought not to call it philosophy at all, since it destroys the very first principles of philosophy.'
These then are the arguments against those who are supposed to follow Pyrrho in philosophy....