The writings of Sextus Empiricus are the only surviving texts that expound the view of the Pyrrhonian Skeptical movement of ancient times. The movement takes its name from Pyrrho of Elis (c. 367-275 b.c.e.), who doubted that there is any way by which one can attain knowledge. He urged that judgment be suspended as to whether any particular assertion is true or false. He argued that to suspend judgment leads to a state of indifference toward the world and to a kind of inner tranquillity that enables one to live at peace in a troubled world.

The actual school of Pyrrhonian thought began much later, in the first century b.c.e. It developed out of the radical Skepticism that had been prevalent in Plato’s Academy under Arcesilaus and Carneades. The Academic Skeptics developed a series of brilliant arguments to show that nothing can be known; they recommended that one live by probabilities. The Pyrrhonists regarded the Academics as too dogmatic, and the former maintained their doubts, even about the skeptical contention that nothing can be known. Starting with Aenesidemus, who had been a student at the Academy, the Pyrrhonian movement developed in Alexandria, primarily among medical doctors. Aenesidemus and his successors set forth a series of arguments against various dogmatic philosophies, including the Academic Skeptics. The arguments purported to show that every dogmatic attempt to gain knowledge leads to difficulties that cannot be resolved. Instead of...

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The Nature of Skepticism

Sextus describes Skepticism as the ability or mental attitude that opposes appearances, the objects of sense experience, to judgments that can be made about them, so that suspense of judgment is achieved and one neither affirms nor denies anything. This state is followed by the state of “quietude,” in which one is untroubled and tranquil. The various dogmatic schools of Hellenistic philosophy—the Stoic, the Epicurean, and the Academic—were all looking for peace of mind, and their theories of knowledge and of the real nature of the universe were intended to lead one to mental peace. The Skeptics contend that the dogmatists never achieve peace because they worry about never knowing whether their theories are true. However, Skeptics, who suspend judgment, achieve peace of mind because they escape such worry.

If Skeptics suspend judgment about everything, how do they live? Sextus answers by declaring that Skeptics accept the world of sense experience undogmatically. It seems to Skeptics that they see certain things, have certain feelings, and so on, but they do not know whether such is really the case. They suspend judgment about all that is not immediately evident to them. Then, without judging, they follow nature and custom, so that—for example—when they seem to be hungry, they eat. They have peace of mind because they do not judge, and they are guided in their lives by their experience, their feelings, and the laws and customs of their society.

The Ten Tropes and More

To achieve this tranquillity, one must first achieve suspension of judgment. Skeptical arguments are offered by Sextus to encourage such suspension. He first offers the ten tropes, or arguments, of Aenesidemus, which show why we should suspend judgment about whether sense objects really are as they appear to be. (Sextus prefaces these and all the other arguments he sets forth with the disclaimer that he is not asserting dogmatically the exact number, nature, or truth of the arguments, but only that it seems to him that they are a set of arguments.) The ten tropes all deal with difficulties in ascertaining when features of our sense experience belong to real objects existing independently of our perceptions.1. Sextus points out, different animals experience things differently according to the nature of their sense organs. We cannot tell which animal has the correct experience. 2. Humans experience the same object differently, and we have no basis for deciding which person has the correct experience. 3. The same object affects different senses in different ways. Honey is sweet to the tongue but sticky to the finger. We cannot tell which quality really belongs to the object. 4. Our impressions of things vary according to our state of mind or our condition. 5. Things appear different from different positions. 6. We never perceive objects individually, but only together with other objects, so that we never know what they are like by themselves. 7. Objects look different...

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The second and third books of Outlines of Pyrrhonism show why Skeptics suspend judgment with regard to knowledge claims in various specific disciplines. The second book treats problems of logic and the theory of knowledge, while the third is a collection of arguments about theology, metaphysics, mathematics, physics, and ethics.

The second book presents the disturbing problem of whether Skeptics can deal with the arguments of the dogmatists without admitting that they, the Skeptics, know something, namely what the opponents are talking about. After contending that he deals only with what seems to be the dogmatists’ view, Sextus turns to what he regards as crucial to any theory of true knowledge, the question of whether there is any criterion for judging what is true. Philosophers disagree as to whether there is such a criterion. To settle the dispute, a criterion is needed, but it is not known whether one exists. Further, any proposed criterion of knowledge would have to be judged by another criterion to tell if it were a true one, and that criterion by still another, and so on.

If the dogmatic philosophers insist that humanity is the judge or criterion of true knowledge, then a problem exists: whether all people or only some are judges of truth. If all, then another criterion is needed to settle disputes among people. If only some, then a criterion is needed to tell which people are proper judges and under what conditions. The...

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Philosophers, especially the Stoics, maintain that they can gain true knowledge by means of signs or inferences that connect what is obvious or evident with that which is not. What is nonevident, Sextus says, falls into one of three categories: the temporarily nonevident, such as that which is on the other side of the wall one is facing; the naturally nonevident, those things that can never under any circumstances be perceived, such as the pores in the skin, but that can be inferred from what is evident; and finally, the absolutely nonevident, whatever can never be known at all, such as whether the number of stars is odd or even. There is a type of sign, called the suggestive sign, which connects what is obvious, our immediate experience, with what is temporarily nonevident. Smoke suggests that there is a fire. Skeptics, like anyone else, accept suggestive signs and act by them, because this is the natural way of relating present experience to possible future experience. However, suggestive signs do not provide true knowledge, only predictions or expectations about the future course of events.

Philosophers hope to gain true knowledge by means of another kind of sign, the indicative sign. This is defined as “an antecedent judgment in a valid hypothetical syllogism which serves to reveal the consequent.” In a syllogism of the form “If A, then B; A, therefore B,” A is an...

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Religion, Metaphysics, and the Sciences

The third book of Outlines of Pyrrhonism rapidly surveys the various sciences from theology and metaphysics to mathematics, physics, and ethics, and indicates that in each of these areas the fundamental concepts are meaningless, that the basic principles are open to question, and that, as a result, one must suspend judgment about whether anything can be known in any of these areas.

Though Skeptics accept the customs of their society and hence its religious views, undogmatically, Sextus points out that the arguments for the existence of God and for atheism are inconclusive, and that the conceptions of God offered by various philosophers are conflicting and often inconsistent in themselves. Further, various...

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When Sextus turns to ethical matters, he points out that philosophers disagree about what is good and bad. There is not even adequate evidence that anything really good or bad exists. The variety of beliefs and opinions about what is good and bad in the various known cultures leads one to suspend judgment about whether there are any objective moral values in the world. (Sextus even points out that some people and some societies condone incest and cannibalism. Who can say that they are wrong?) Skeptics live undogmatically, not judging whether things are good or bad, but living according to the dictates of nature and society. Skeptics, like others, may suffer from physical pains, but they will avoid the additional mental suffering...

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Additional Reading

Barnes, Johnathan. The Toils of Scepticism. Cambridge, London: Cambridge University Press, 1990. This is a technical but clear and engaging exposition of Pyrrhonian Skepticism by one of the foremost Oxford philosophers. Includes bibliographical references.

Hookway, Christopher. Scepticism. London: Routledge, 1990. Chapters 1 and 2 give a general account of Pyrrhonian Skepticism through the view of Sextus Empiricus. The rest of this book contains a detailed account of the influence of skepticism in various areas of modern philosophy.

Popkin, Richard H. The History...

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