We know almost nothing—about Sextus Empiricus. We do not know when this codifier of Greek skepticism was born or when he died. We do not know where he was born or taught or even if he was Greek rather than a barbarian. He appears to have been a physician and the head of some school of philosophy. Most scholars place him in the second century. But they are guessing.
What we do know is that Sextus Empiricus authored Outlines of Pyrrhonism and Against the Logicians. These books, along with several others that are commonly attributed to him, compile two hundred years of skeptical arguments. Since Sextus wanted to counter the dogmatists of his day, he patiently describes the doctrines of Aristotle, Diodorus Cronus, the Stoics, and many others. Sextus only records philosophical positions with a view to undermining them. Ironically, Sextus’s survey of sites slated for demolition is much responsible for their preservation. Like the other accidental historian of ancient philosophy, Diogenes Laertius, Sextus’s works were widely and persistently circulated because he had a flair for paradoxes.
Sextus leaves us uncertain as to his specific brand of skepticism. Sextus has long been construed as advocating suspending judgment on all matters. The ancients knew that the Pyrrhonists were inspired by Pyrrho of Elis. Diogenes Laertius reports that Pyrrho learned his philosophy in India. Pyrrho could have visited India by tagging along with Alexander the Great’s expedition. Scholars have pointed out several features of Pyrrho’s philosophy that seem alien to Greek philosophy and that were indigenous to Indian philosophy. Diogenes also reports that since Pyrrho trusted no belief more than any other, he went “out of his way for nothing, taking no precaution, but facing all risks as they came, whether carts, precipices, dogs or what not.” (1925 II, 61-62) Nevertheless, Pyrrho managed to reach age ninety because of the many students and friends who “used to follow close after him.”
Sextus treats philosophy as a kind of mental disorder that can be quieted by dialogue. As physicians are wont to do, Sextus presents his cure as a serendipitous discovery. Like other seekers of the truth, the skeptic began as a dogmatist frustrated by his failure to solve the paradoxes. Weary, he lapsed into a state of suspended judgment. Ironically, this doubt relieved him of the anxiety that he had hoped to dispel by finding the truth. Sextus recalls the story of Apelles, who was trying to paint the mouth foam of a horse. This famous painter used a sponge to clean the paint from failed efforts. Apelles became so frustrated that he threw the sponge at the picture. To his surprise, the mark left by the sponge produced the effect of the horse’s foam. Similarly, the skeptic unintentionally happened upon a resolution of problems that vexed him. Pyrrhonism consolidates this dumb luck.
Sextus’s basic strategy is to treat inconsistency as a tranquilizing ally rather than as an adversary. When you find yourself becoming opinionated on a topic, try to think of opposing arguments. As the pros and cons cancel out, peace of mind dawns.
This method of equipollence must be understood psychologically. It would be dogmatic to rate one argument as being equally cogent as another. Sextus’s aim is to balance the persuasive force of the arguments, not their real merits. The persuasive force is gauged passively, by noting how the argument affects the subject in question. In one’s own case, it is difficult to separate one’s opinion of the argument’s cogency from its objective logical force. Self-therapy gives you no psychic distance. But when Sextus is curing others, he can freely tailor his talking therapy to the patient in question. The skeptic
. . . desires to cure by speech, as best as he can the self conceit and rashness of the dogmatists. So just as the physicians who cure bodily ailments have remedies which differ in strength, and apply the severe one to others whose ailments are severe and the milder to those mildly affected—so too the skeptic propounds arguments which differ in strength and employs those which are weighty and capable by their stringency of disposing of the Dogmatist’s ailment, self conceit, in cases where the mischief is due to severe attack of rashness, while he employs the milder arguments in the case of those whose ailment of conceit is too superficial and easy to cure, and whom it is possible to restore to health by milder methods of persuasion.
(1933a, III, 289-91)
Sextus is interested in what is the effect of an argument rather than what ought to be the effect. He calmly narrates the experience of deduction just as Albert Hoffman relates the phenomenology of lysergic acid diethylamide (LSD) in his 1943 “Laboratory Notes.”
Sextus’s method of titrating arguments with counterarguments must be exercised on a laborious case-by-case basis. Conveniently, Sextus also prepares all-purpose argument patterns that help the patient argue other positions to a draw. As the patient becomes a well-rounded dialectician, he absorbs the lesson that “reason is a such a trickster” and stops taking philosophical arguments seriously.
Sextus cannot assert the therapeutic philosophy outlined above. Anyone who asserts a proposition implies that he knows it is true. Accordingly, Sextus severely hedges his philosophical remarks. To cover occasional lapses, he peppers his writings with blanket disclaimers:
For, in regard to all the Skeptic expressions, we must grasp first the fact that we make no positive assertion respecting their absolute truth, since we say that they may possibly be confuted by themselves, seeing that they themselves are included in the things to which their doubt applies, just as aperient drugs do not merely eliminate the humours from the body, but also expel themselves along with the humours.
(1933a, 1, 206–7)
Sextus advertises Pyrrhonism as a way of life rather than a doctrine.
Pyrrhonism differs from the Academic Skepticism that flourished after Arcesilaus took over Plato’s Academy. The greatest representative of the new academy, Carneades contended that knowledge is impossible. The Stoics had objected that doubt is paralyzing. One does not know what to do next. The skeptics of the new academy replied that decisions can be made on the basis of probabilities (of a qualitative character, not the numeric sort introduced by Pascal and Fermat in the seventeenth century).
Some propositions are more justified than others. Many contemporary scientists are mitigated skeptics of this cautious sort. They are fallibilists who think we can be mistaken about anything. By a testable mixture of observation and theory, scientists instead assign probabilities to hypotheses. As new evidence comes in, the probabilities are revised. Science is a raft that is constantly being repaired. No part is essential. The raft is kept afloat by the process of revision.
Sextus denies that the Academic Skeptics are entitled to assert the sweeping generalization “Knowledge is impossible.” A proof that “There is no proof whether p is true” tends to be more demanding than proof of a typical theorem. To prove a conclusion, one need only find a single cogent argument for it. To prove that p can be neither proved nor disproved, one must prove the universal proposition that there are no such arguments for p and no such arguments for not p. Universal propositions impose a heavier burden of proof than singular propositions. Consequently, the assertion that “Knowledge is impossible” merely substitutes negative dogmatism for positive dogmatism.
More radically, Sextus thinks it is dogmatic to affirm that probability is the guide of life. To change your mind on the basis of probabilities, you need to assign some probabilities prior to any inquiry. These prior probabilities are assigned without any reason. But then one is assigning some propositions higher status than others without any basis. This favoritism is dogmatic. Sextus casts himself as the open-minded inquirer who refuses to acknowledge that any belief is more probable than any other. Since he does not want to commit himself to any proposition, he does not want to assert that we lack knowledge. For all we know, we know as much as we seem to know.
Since Sextus is unwilling to assert premises, he can only mount indirect arguments. In reductio ad absurdum and conditional proof, one merely supposes a premise. Sextus lets the premises be the dogmatist’s beliefs and then confines himself to internal criticisms in which he exposes contradictions or shows that his adversary’s position has implausible consequences. Sextus does not seek decisive arguments that will convert his adversary from being a believer to being a disbeliever. After all, disbelief is just belief in the negation of a proposition. Sextus encourages neutrality rather than disbelief. He does not want to win or lose; he only wants to play long enough to show the futility of the game.
Sextus opposes philosophical beliefs, not the ordinary beliefs one has in everyday life. Sextus encourages us to follow appearances, to abide by local customs and laws. This conservatism includes religious observances—as long as this piety does not froth over into religious metaphysics and fanaticism. To get along, go along.
Sextus is free to claim knowledge in his ordinary dealings with people. If he is challenged by a philosopher, the conversation becomes philosophical and Sextus will retreat to the claim that it appeared to him that he had knowledge.
Many of Sextus’s arguments are specific objections directed against the live options of his day: Stoicism, Atomism, Aristotelianism. He called one of his most effective general arguments “the wheel.” If you want to sort good apples from bad apples, then you need a criterion. But how do you know that the criterion correctly classes the good apples as good and the bad apples as bad? It seems you could only know the criterion is accurate if you already know which apples are good and which are bad. But if you know that, you do not need the criterion!
Now consider the problem of sorting good beliefs (justified beliefs or knowledge) from bad beliefs. To know whether the criterion is accurate, one must be able to independently sort good beliefs from bad beliefs. But if one could sort them without the criterion, then the criterion is redundant.
The problem of the criterion locks into a classic infinite regress. The following four propositions about justification seem plausible but are jointly inconsistent:
1.Some beliefs are justified.
2.A belief can only be justified by another justified belief.
3.There are no circular chains of justification.
4.All justificatory chains have a finite length.
Much of epistemology can be seen as an attempt to extinguish this paradox about the regress of justification.
Epistemological anarchists reject 1, the assumption that some beliefs are justified. This position is self-defeating because it implies that “No beliefs are justified” is itself unjustified. Notice that anarchism is incompatible with Carneades’ probabilism. Although Sextus cannot assert that no beliefs are justified, he nudges his reader toward arguments that imply that conclusion.
Foundationalists reject 2, the requirement that every justified belief be grounded by another justified belief. The Stoics contended that some perceptual judgments are self-evident truths. This made them the butts of practical jokes. After hearing Sphaerus the Stoic deny that a wise man assents to mere opinion, King Ptolemy Philopator secretly placed waxen pomegranates on the dinner table. When Sphaerus reached for one, the king invited all to conclude that even a wise man might assent to a false presentation.
Sextus embarrasses foundationalists by exhibiting their disagreements as to which truths are self-evident. The foundationalists look dogmatic because of their refusal to defend their self-evident propositions with argument.
Coherentists reject 3, the prohibition against circular reasoning. They agree that one cannot justify a proposition by arguing in a small circle, such as “Sextus was a contemporary of Galen, therefore Sextus was a contemporary of Galen.” But they think that some large circles justify a belief. Nelson Goodman (1954) has characterized the method of reflective equilibrium as virtuously circular: We formulate a general principle and see whether it conforms to our judgments about particular instances. When we discover a conflict, we must decide whether to retain the principle or our opinion about the particular case. If we amend the principle, we go on to consider other cases. We work back and forth between principles and particular cases trying to get a better and better fit. This process justifies the beliefs we have reflected upon even though we have been reasoning in an expanding ring.
Infinitudists reject 4, the requirement that all justificatory chains be finite. The first and almost only philosopher to espouse this position was Charles Pierce (1839-1914). Most philosophers think finitely long chains of justification provide no practical escape from anarchism: Finite thinkers do not have enough time to form infinite chains. Therefore, the theory implies that finite beings lack any justified beliefs.
A direct argument infers a conclusion from an asserted premise. Sextus questions whether direct arguments can rationally persuade anyone. In Against the Logicians, he contends that all direct arguments must either encourage a hasty inference or be superfluous:
By what means, then, can we establish that the apparent thing is really such as it appears? Either, certainly, by means of a non-evident fact or by means of an apparent one. But to do so by means of a non-evident fact is absurd; for the non-evidence is so far from being able to reveal anything that, on the contrary, it is itself in need of something to establish it. And to do so by means of an apparent fact is much more absurd; for it is itself the thing in question, and nothing that is in question is capable of confirming itself.
(1933b, II, 357)
Socrates exhorts us to follow the argument wherever it leads. But if “follow” implies belief, this is bad advice. To ignore the plausibility of the conclusion is to waste a clue about the reliability of the argument. Such profligacy is irrational because it violates the requirement that belief be based on the total available evidence. The implausibility of Socrates’ conclusions provides ample reason to doubt the cogency of his arguments. Sextus makes a sensible comparison: “For just as we refuse our assent to the truth of the tricks performed by jugglers and know that they are deluding us, even if we do not know how they do it, so likewise we refuse to believe arguments which, though seemingly plausible, are false, even when we do not know how they are fallacious.” (1933a, II, 250)
We associate such circumspection with promoters of common sense! For instance, G. E. Moore (1873-1958) appeals to the principle of weighted certainties. Moore was impressed by subtlety of skeptical arguments and frequently found it difficult to pinpoint a fallacy. Nevertheless, he was sure there had to be a flaw somewhere because the conclusion was obviously false. For example, many skeptical conclusions implied that he could not know that a particular object was a finger.
It seems to me a sufficient refutation of such views as these, simply to point to cases in which we do know such things. This, after all, you know, really is a finger: there is no doubt about it: I know it and you all know it. And I think we may safely challenge any philosopher to bring forward any argument in favor either of the proposition that we do not know it, or of the proposition that it is not true, which does not at some point, rest upon some premise which is, beyond comparison, less certain than is the proposition which it is designed to attack.
(1922, 228)
Moore seems to assume that proof yields a fresh belief only when unopposed by an entrenched belief. In other words, a proof can only be persuasive when it pushes into a blank area, not when it must displace preexisting belief or disbelief. But why should belief always spread into neutrality but never vice versa? Neutrality is not a void that lacks any positive causal power. When a traveler on a tight schedule comes to neither believe nor disbelieve that he is on the right road, that neutrality topples his belief that he will arrive on time.
However, we must concede to Moore that there is nothing irrational or illogical in distrusting arguments that lead to strange conclusions. Indeed, the textbook technique of refutation by logical analogy rests on the legitimacy of harnessing our knowledge of conclusions as a test of the cogency of arguments. The technique is a sign of our logical modesty; our past troubles with fallacies and sophisms and the many logical errors of peers provide ample inductive grounds for caution. Logical analogy can also be viewed as an application of the widely accepted methodology of reflective equilibrium. Rules are to be checked against the intuitive acceptability of the particular inferences they allow or disallow. If the rule leads us from intuitive truths to intuitive falsehoods, the rule is ripe for rejection. Thus, orthodox logical methodology endorses peeking at the conclusion.
The Socratic commandment forbids us from appealing to the implausibility of the conclusion when explaining what is wrong with an argument. This strategy is compatible with acknowledging the relevance of the conclusion’s plausibility. When an editor keeps the identity of an author secret from a referee, the editor can admit that the knowledge of the author’s identity is relevant in appraising the manuscript. The author’s reputation is a fast and fairly accurate indicator of the quality of the manuscript. The editor is free to use this information at a later stage of her deliberations. However, she does not want her referee to use the author’s identity as a mental crutch and she does not want him to be biased. The editor wants the referee to focus on the manuscript itself.
Similarly, philosophers want us to wear blinders when trying to pinpoint the flaw in a paradoxical argument. If there really is something wrong with the premises or the reasoning, we should be able to locate the problem without relying on knowledge of the conclusion. Like any diagnostician, the philosopher wants the failure to be predictable from features of the original situation.
A little logical humility is a good thing. But how are we to prevent Sextus from expanding our caution into logical paralysis? The question has been deepened by a puzzle that Gilbert Harman (1973, 148) attributes to Saul Kripke. Suppose I believe that my friend Ted drinks and you try to dissuade me: “Ted has an allergy to alcohol, so since no one with such an allergy drinks, Ted does not drink.” I am unmoved. I reveal my reasoning:
1.Ted drinks.
2.If Ted drinks, then if you present a valid counterargument that implies Ted does not drink, then that counterargument has a false premise.
3.Therefore, if you present a valid counterargument to “Ted drinks” that implies Ted does not drink, then it has a false premise.
4.You have presented such a valid counterargument to “Ted drinks.”
5.Therefore, your counterargument has a false premise.
By hypothesis, I believed the first premise prior to your counterargument. I also fully believed the second premise because it is analytically true. Since the third statement follows by modus ponens, I took this warning to heart. By advancing your counterargument, you make the fourth premise obvious to me. Conjoining it with the third yields the final conclusion by another modus ponens inference. This metaargument can be generalized to yield Sextus’s conclusion that no one can be rationally persuaded by a direct argument.
Sextus was aware that it seems too self-defeating to argue that nothing can be justified by argument. However, “Nothing can be justified by argument” is not a contradiction; nor is there any contradiction in “Sextus argued that nothing can be justified by argument.” Since both these sentences are consistent, Sextus does not feel pressure to disavow them. Anyone who hopes to score off of this paradox is merely engaged in rhetoric.
Of course, Sextus is not one to draw a sharp distinction between rhetoric and logic. The next chapter is devoted to a rhetorician who blurs this line with pragmatic paradoxes.