Pyrrho (360 – 270 BCE), the greatest skeptic of ancient Greece, was from Elis, Northwest of Athens on the Dorian peninsula.  Diogenes Laertius says that Pyrrho was originally a painter, an interesting profession for a thinker who argues that reality is appearances and human judgements are images that never fully capture the original.  Originally, the word ‘skeptikos’ meant ‘inquirer’, someone who investigates matters continuously.

As we have discussed with previous thinkers such as Xenophanes, Heraclitus, Democritus and Socrates, skepticism is often portrayed by more dogmatic thinkers as a pessimistic nihilism, a dreary attitude that no knowledge is possible, but skeptics are often quite optimistic about seeking wisdom within oneself and throughout the cosmos.  While skeptics are relativists, critical of claims to absolute universal knowledge, skeptics are passionate about seeking relative truth, which they argue is a continuous source of insight and engagement.  Clearly, “inquirers” believe that there is no end to inquiry, no end to what we can discover.

Democritus pinting

As a young painter, Pyrrho became fascinated with philosophy through the works of Democritus, the atomist who was quite skeptical of human judgements in spite of his atomic theory.  Democritus said, “Reason is a powerful persuader”, and about the gods and the workings of the heavens, “Man is what we know”.  Critical of knowledge, said we should have much thought rather than much learning, and said, “In reality, we know nothing, for truth is in the depths”, arguing that we must remind ourselves that we are always relatively removed from the reality that surrounds us.  This is similar to Heraclitus, who wrote, “Nature loves to hide”, and “Things keep their secrets”.  Also, like Heraclitus, Democritus said, “The world is change, life is opinion”, and “The world is a stage, life is our entrance: You came, you saw, you left”.  Pyrrho also was acquainted with the paradoxical thought of the Eleatics, which he learned from the Megarian School, founded by a follower of Socrates.

Jain statue vines karnataka

Pyrrho traveled with his teacher Anaxarchus, also a follower of Democritus, and Alexander, student of Aristotle and emperor, to Persia and India, some sources say as a soldier and others as a scholar.  Alexander failed to conquer India, unlike he had Egypt and Persia.  It is said that Pyrrho learned from the Persian Magi as well as Indian ‘gymnosophists’, a strange term meaning those who trained and studied both gymnastics (likely yogic postures) and philosophy.  These could have been Jains, who were known for logical debate as well as extreme practices of bodily discipline, sometimes fasting while standing in the jungle for days.  Statues of Jain teachers frequently show vines growing up their very naked bodies.  Sources say that one Indian gymnosophist set himself on fire to go willingly to death, terrifying Alexander and his entourage.

Pyrrho Woodcut

After returning to Elis, Pyrrho chose to live a simple life of poverty, but he was known both in Elis and in Athens for his skill at debate, and the Athenians went so far as to offer him citizenship and construct a statue to his honor after his death.  The people of Elis offered Pyrrho the job of chief priest, believing his command of truth to be divine, and to honor him made philosophers exempt from taxation.  Pyrrho wrote nothing, though his work was recorded by his student Timon (not the meercat of The Lion King), and then his skepticism was elaborated much later by Sextus Empiricus, from whom we know of Pyrrho’s thought today.


Jains, good candidates for the gymnosophists Pyrrho met in India, advocate two principles that are shared with Indian thought but credited to Jain innovation: anekantavada, the multiplicity and relativity or “non-one-endedness” of reality, and syadvada, the hypothetical and imperfect nature of perspective and judgment that is always the fiber of human truth.  According to these two principles, all human beliefs and judgments are temporary and partial views of each particular thing, including the self and the cosmos.  Jains, like Buddhists, believe that things may or may not be as they seem and may or may not be expressible as they are.


Pyrrho’s skepticism is summed up under the term ‘acatalepsia’, withholding judgement.  Like Zeno, Pyrrho taught that any belief can be countered by the opposite belief which contradicts it.  Thus, like Jains, Pyrrho held that reality is not one-sided, like human judgements, and that all judgements are partial and should be treated as hypothetical, as a best guess.  While some in ancient or modern times might accuse Pyrrho of being a sophist, of being a destroyer of truth who merely argues any side skillfully but without genuine pursuit of the truth, Pyrrho, like the Eleatics and Socrates, believed that seeing the limitation and contradictions inherent in all sides of the truth, in all positions of human judgement, brings one closest to the full truth, giving one the god’s eye view, as far as mortally possible.  Recall that Aristotle said that skeptics are no better than plants, preferring universal certainty.

Raphael Parmenides

Just as Socrates’ knowledge that we mortals are ignorant was considered divine (as we saw in Plato’s Apology and Symposium), Pyrrho, like Parmenides in Plato’s dialogue of that name, argued each side knowing that each side was ignorant and limited.  Just as Socrates in Plato’s Meno argued that we can pursue the good, though we do not know what it is, both knowing and not knowing it, Pyrrho put this into practice like Parmenides, showing that each side of any argument is simultaneously a knowing and not knowing, both true and false, as is the opposing side.  As evidence of this, Pyrrho pointed to the continuous fact of differences of opinion amongst both the foolish and the wise, constant argument among both the educated and uneducated, the common and the distinguished alike.

Nagarjuna print

Pyrrho argued that each thing is both this and that, and neither this nor that.  This is very similar to the great Buddhist logician Nagarjuna, who argued that each thing or judgement is, is not, both is and is not, and neither is nor is not.  Consider the example of a fire being hot.  Because a particular fire is not simply hot, but only relatively hot (cooler than the plasma in a star, for example), it is also correct to say that the fire is not hot, insofar as it is not simply or entirely hot.  Similarly, then, it is also correct to say that the fire both is and is not hot, both to a particular extent.  Finally, because the fire is not simply or exclusively hot or not hot, it is correct to say that the fire neither is nor is not hot.

Plato and Aristotle

Recall that Plato’s Parmenides told Socrates that if one practices this sort of dialectical exercise, one will grow wise and come to see the truth of the forms of things.  Pyrrho may very well have found this sort of exercise in debate with Indian logicians and brought it back to Elis, even though it already existed in Athens in the works of Plato.  Legend has it that Pyrrho could defeat anyone in argument, then take his opponent’s position and defeat his own.  He could do this because he knew that human truth was fundamentally one-sided, and so could not eliminate opposition.

Early Gandhara Buddha

Pyrrho believed that seeing this theoretically and then putting it into practice, exercising as Plato’s Parmenides suggests, brings peace of mind and freedom from fear, what Pyrrho and later Pyrrhonians called ‘ataraxia’, a state of tranquility.  If one is attached to neither side of an argument, then one has nothing to fear if either side is asserted or denied.  Because things are non-one-sided, appearing to us as one-sided but then as two-sided, we must ask ourselves what our relationship is to the truth and how we should approach life.  Pyrrho believed in a life of simplicity and being emotionally detached and at peace, similar to Greek philosophers we have already studied, as well as the Epicureans and Stoics we will study next week, who while disagreeing with Pyrrho also believed that the practical goal of life was attainment of ataraxia.  It is also very similar to Buddhism, which took much from Jainism.

Mountain range china

Some sources, critical of Pyrrho, said that wherever he went he needed to be chaperoned by friends so that he would not skeptically try to walk off the sides of cliffs or in front of chariots and wagons.  It is likelier that Pyrrho could argue that one could pass through a chariot or walk through the air without feeling it necessary to prove this physically, and this story was told by more dogmatic thinkers who Pyrrho angered with his skepticism.  It is true that no chariot or wagon is absolutely solid, nor is walking off a cliff certain death.  While Pyrrho argued that our understandings are mere appearances, this does not mean that one should act as if appearances are entirely unreal.


Aenesidemus founded Pyrrhonism or Pyrrhonian Skepticism as a school in the first century BCE.  Continuously angering more dogmatic thinkers and schools of thought, Pyrrhonians were known for relativising every assertion with, “It seems that…”, or “It appears to me that…”, rather than state categorically what is the truth.  Critical of the logic of Aristotle and his Peripatetic school, the Pyrrhonians argued that there were no truths that could be absolutely asserted (All X is Y) or absolutely denied (No X is Y).  All that we can know, given our limited perspective and ability to gather knowledge through experience, is what can be relatively asserted (Some X is Y) or relatively denied (Some X is not Y).  Here, there is an interesting difference between our use of the terms ‘general’ and ‘universal’, both of which Aristotle applied to absolute assertion and negation.  When we say ‘universal’, we mean absolute, but when we say ‘general’, this can also mean relative.  Thus, for Aristotle, to say, “X is generally Y” means X is always Y, but we can read that as saying, “X is relatively and mostly Y”.  While Pyrrhonians did not deny this second sort of statement, asserting or denying something predominantly, they would deny Aristotle the ability to make universal statements, which he would also call ‘general’ statements.

Skepticism between Pyrrho & Sextus: Timon & Aenesidemus


Between the death of Pyrrho in 270 BCE and the time of Sextus Empiricus, four hundred years later, there is limited evidence of a Pyrrhonian tradition.  While Pyrrho wrote nothing, Pyrrho’s student Timon, who lived with Pyrrho for many years in Elis, left behind fragments of poetry found in the works of other philosophers and historians.  Timon wrote that what our senses and mind tell us, our sensations and conceptions, are neither lies nor truth, but both and neither.  Realizing this as theoretically true and then putting it into practice results in speaking less, freedom from fear, and happiness.


The next Pyrrhonian was Aenesidemus, who took up Pyrrho and Timon’s skepticism in Alexandria Egypt in the first century CE.  This leaves a gap between the death of Timon, around 230 BCE, and Aenesidemus, who was living after the year 0.  Clearly the works of Timon, and possibly other followers of Pyrrho, had survived.  Alexandria was the capital of Alexander’s empire, which he chose to place in Egypt, and it remained one of the greatest centers of ancient knowledge for centuries.  It’s library, known as the Library of Alexandria, was said to contain all the texts of the ancient world that could be acquired, many having been looted by Alexander and his armies.  Unfortunately, the library, which turned out to have been a set of thousands of scrolls on a long shelf and not a separate building as archeologists originally supposed, was burned by Julius Caesar in 48 CE, some say accidentally and others intentionally.


Aenesidemus’ major work, Pyrrhonian Discourses, did not survive.  He is known to have argued against members of Plato’s Academy and Stoics about beliefs they strongly asserted, even as they admitted degrees of skepticism.  Like a Jain or Buddhist logician from India, Aenesidemus argued that things could be quite true at certain times and places, but quite untrue at others, and human conceptions were incapable of revealing more than this to us.  He was known for arguing this with his ‘Ten Tropes’, ten recurring themes or points he often made.  These ten were:

1) Various animals perceive things differently.

2) Various people perceive things differently.

3) One person can perceive things differently, as contradictory.

4) Perception varies from one time to another.

5) Perception varies from one place to another.

6) Things are perceived through media, such as air and water.

7) The things we perceive change continuously in size, color and temperature.

8) Perceptions are relative and interact with each other.

9) Perceptions become weaker after repetition, becoming custom.

10) People are raised in various cultures, under various laws and customs.


Like the modern Scottish philosopher Hume, who will be mentioned again soon, Aenesidemus argued that cause and effect cannot be known physically but only via mental conception.  The mind witnesses two events, and links the two together with a concept, which then becomes a customary prejudice.  While it is useful to assume that things will follow in accord with one’s conceptions, this may, for all we know, only be true under certain circumstances but not others.

Raphael Heraclitus

Aenesidemus was also a follower of the work of Heraclitus, who argued that opposites codetermine each other and can both be present at one and the same time in the same thing, unlike Aristotle.  Many of the ten tropes are similar to the thinking of Heraclitus, who also argues that things are variously perceived using the example of various animals and various cultures, and who argues that all things change unceasingly.

Sextus Empiricus

Sextus Empiricus

Sextus Empiricus (160 – 210 CE) is the first Pyrrhonian Skeptic whose text survives today, the major work by which Pyrrho, Aenesidemus and Pyrrhonian Skepticism are known.  Sextus uses the terms ‘skeptic’, ‘Pyrrhonist’ and ‘Pyrrhonian’ interchangeably.  His major work can thus be variously translated as Outlines of Skepticism or Outlines of Pyrrhonism, both titles existing in print today as the same text.  Sextus is heavily influenced by Aenesidemus, and he places the ten tropes centrally in the beginning of his Outlines.  Several other works of Sextus’ survive, typically gathered under the title Against the Professors, which include Against the MathematiciansAgainst the AstronomersAgainst the RhetoriciansAgainst the MusiciansAgainst the EthicistsAgainst the LogiciansAgainst the PhysiciansAgainst the Physicists, and, most centrally, Against the Dogmatists.


Sextus was likely a doctor who lived in Alexandria, Egypt, thought this is disputable, as some sources place him in Athens, and others in Rome.  Various sources, including the famed doctor Galen, report that Pyrrhonian Skepticism was popular among many in the medical profession, as it was always possible to be wrong about a diagnosis and change treatment depending on outcomes.  This remains so today, in spite of the fact that medicine is perhaps the most important and practical of the sciences for our survival.

sextus empiricus outlines of pyrrhonism

Sextus’ Outlines of Skepticism is composed of three books.  The first book is a general argument for the skepticism of Pyrrho and Aenesidemus, including Aenesidemus’ ten tropes.  The second and third books are specifically concerned with attacking particular opponents’ positions, the second book focusing on epistemology and logic, on how we know and how we argue, the third book on physics and ethics, what we know about the cosmos and the individual.

Sextus begins saying that in any matter being investigated, we could either A) assert we have found the truth, B) deny that any truth can be known, or C) continue to investigate.  The first is dogmatism, which includes Aristotle, Epicurus and the Stoics.  Sextus says early in the work that the Stoics are his chief dogmatic opponents.  The second is the position of Academics (of Plato’s Academy) such as Clitomachus and Carneades.  The third position is that of skeptics, who continue to investigate and describe things as they appear.  Pyrrho is the first, according to Sextus, to have systematically and thoroughly committed himself to skepticism.  The second position, a pessimistic skepticism Sextus identifies with members of Plato’s Academy long after the time of Plato, is not for Sextus genuine skepticism, but a dogmatic position that knowledge and truth are completely impossible.

Zhuangzi contemplates tree

Sextus says that by suspending judgement, we can achieve tranquility.  Clearly, this suspension of judgement is not a suspension of investigation, and neither is achieving tranquility.  Judgement is suspended such that more investigation is possible, and the tranquility achieved is an opening of the individual mind to the greater pursuit of truth.  Skepticism is the development of an ability to investigate, an ability hindered by all dogmas.  In the Chinese Daoist text the Zhuangzi, we read similarly, “You cannot discuss the way of things with a cramped scholar, as he is shackled by his doctrines”.


Sextus says that skepticism is the ability to think.  When we take a position on a matter dogmatically, we are limiting ourselves from taking the contrary position, from thinking that which contradicts our position.  If we find a position to be quite true, and then take it up as our position, we block ourselves from taking the opposite position, which may also be true in other ways, times or places.  For this reason, the best position is to have no particular position, realizing that various positions can coexist complexly in ways that dogmatic systematization cannot capture.  Pyrrhonians, unlike any other school, develop this ability to its utmost, and thus achieve a calming of the soul.  Other schools sought truth dogmatically, thinking that they would achieve tranquility once they found what is simply true and what is simply false.  Unfortunately for dogmatists, for every position there is a counter-position, for every truth there is a counter-truth.  Recognizing this, Pyrrhonians hold no beliefs as absolute, and thus can freely assert or deny any position as needed.

Pyrrho Ship of Skeptics

While Pyrrhonians hold no beliefs, this does not mean that they do not have impressions or cannot give descriptions.  To believe one’s beliefs are true is to assert something that is unclear, unlike impressions and descriptions, which can be clearly given even if they are never absolute.  This is not to say that everything is false dogmatically, as this would not be suspension of belief.  Rather, one should describe one’s own impressions, without feeling the need to extend these impressions into beliefs.

pythagorean teaching

Sextus says that Pyrrhonism is not a school if a school is defined by its beliefs, but if a school is an orientation on how to live life and think, then Pyrrhonism is a school.  Notice that this makes Pyrrhonism both a school and not a school, and so it is also neither a school nor not a school exclusively.  Pyrrhonians, like those of other dogmatic schools, should study the natural sciences, but primarily such that all dogmatic beliefs can be opposed, not to assert dogmatic belief about any subject.  The same is true of Logic and Ethics.

Nietzsche painting munch

If skepticism rejects beliefs, can it say nothing?  Sextus says that things do appear to be the case, and that the way things appear should continue to be investigated.  Just as things are perceived differently by various animals, and perceived differently at various times and from various positions, the way that things do appear to ourselves and others is investigated by the skeptic.  It is granted that there are perceptions, that there are appearances, but these themselves appear to be true and appear to be untrue.  While dogmatists argue that skeptics reject what is apparent, Sextus argues that skeptics rather show that dogmatists are rash in accepting appearances as truth, which is done by neither accepting nor rejecting appearances.  Like dogmatists, skeptics have standards, but their standards are not convictions but processes, not statements about reality but activities of investigation.  Neither dogmatists nor skeptics can be entirely inactive.  We all naturally perceive, think, desire, value, and teach.  Sextus says that this can all be done skeptically, without convictions or dogmas.


Like Aristotle, Sextus argues that all things have their aim or purpose, the object of desire.  Skepticism aims at tranquility and moderation.  While Aristotle argued for the achievement of purpose and moderation, unlike Sextus and skeptics Aristotle aimed for universal truths uncontradicted by genuine opposition.  Sextus argues that skeptics too seek truth and act towards aims, but they are enabled by the tranquility achieved through suspension of judgement, of moving beyond the aim for uncontradicted truths.  Dogmatists must commit themselves to deciding whether particular things are good or bad by nature with an intensity that prevents them from thinking, feeling and acting in moderation.  It is indeed an odd paradox in the philosophy of Aristotle that his logic proceeds from the principles of noncontradiction and the excluded middle, the exclusive separation of true and false, but his ethics is centered on the mean, on the inclusive balance of extremity and disparity, of excess and lack.  Sextus is arguing that we would best attain Aristotle’s ethics by avoiding Aristotle’s logic.  Similarly, we attain greater truth, are more enabled to seek truth, by avoiding dogmatic judgements and convictions.

Minimalist Painting Smiber

Sextus tells us a story to illustrate.  Apelles, a painter (like Pyrrho) was trying to paint the lather of a horse’s mouth, but after trying again and again he could not.  Out of frustration, without thinking, Apelles flung his sponge for removing paint at the image of the horse, and accidentally it produced the perfect representation he had been seeking all along.  This has remarkable parallels with the birth of modern art with the Dada and Surrealist artists, who used automatism to create their works.  Recognizing, like ancient Pyrrhonians, that rational planning was actually a process that is not entirely under our own control, they would create works “automatically” by following a methods that randomly produced works that became spontaneously beautiful, created and not created by the artist simultaneously and seamlessly.


This fluid and effortless creation is the aim of skepticism too, but achieved in thought the way that a great painter achieves it in paint.  Skeptics, like everyone else, are disturbed by things such as cold and thirst, but unlike many they act without thinking they must aim at convictions, at uncontradicted judgements, and so are more capable of acting in moderation when disturbed.  Investigating things flows freely when we do not need to bring it to final exclusive judgements.


How are we to suspend judgement?  Sextus says that it comes about through opposition, opposing appearance against counter-appearance and opinion against counter-opinion, “crosswise” as Sextus puts it.  As an example, he gives a tower which has flat sides appearing round from a distance.  We can consider another similar example (from an educational children’s show I watched when I was young) that from the side a pyramid and cone appear to be triangles, but from above the pyramid appears as a square and the cone as a circle.


As another example, Sextus says that against those who believe in providence, that the cosmos is ordered such that the good will gain and the bad will lose, can be opposed examples of “the good doing badly and the bad doing well”, by which it appears that there is no providence or cosmic order.  Recall that these are the two opposed views of Socrates and Thrasymachus in Plato’s Republic, and that Socrates opposed Thrasymachus but did not feel satisfied and after Thrasymachus, himself unsatisfied and frustrated, left the gathering, Socrates proceeded to oppose Thrasymachus’ position with Plato’s own dogmatic form of justice and virtue.  Sextus, without mentioning the Republic, is not saying that we should be convinced that Thrasymachus is right, that there is no cosmic order and power is simply the good of the stronger, but rather that each position has a counter-position, and we should abstain from being convinced that either is exclusively right.  This would mean that, rather than oppose Thrasymachus’ pessimistic skepticism with dogmatism, we should maintain skepticism, like the original Socrates, but be unattached to either optimism or pessimism, uncommitted to the conviction that things do or do not work out for the good.

eagle eye

Sextus presents the ten tropes of Aenesidemus at length, cautioning that this is not a list of all possible modes, nor should it imply that each of these is equally powerful in particular circumstances.  He gives many examples, which may or may not be his own or those of skeptics before him.  Animals with different eyes will perceive colors differently, and some animals can see in the dark.  Colored lights and curved mirrors change appearances.  Food becomes various parts of animal bodies, as water becomes various parts of plants.  Different finger positions make the breath through a flute and the string on the lyre produce high and low notes.  Unlike humans, insects hate perfume and olive oil.  Sextus includes examples given by Heraclitus, that seawater is drinkable by fish and pigs bathe in mud.

jumping dog

Sextus says that, unlike the “deluded and self-satisfied dogmatists”, who ridicule animals and those they disagree with as “irrational”, skeptics know to compare the various ways of animals, similar and different from each other, to the various convictions of humanity.  Several times Sextus says “the so-called irrational animals”, indicating that he is skeptical of the distinction.  In a move sure to please Diogenes, Sextus argues that even dogmatists must admit that dogs, often thought to be the lowest of animals, is far more capable than humans at perception through sight, sound and smell.  Dogs are great hunters and courageous defenders.


Like animals, humanity has various minds and bodies, and thus has various opinions and feelings.  Sextus uses the example of comparing the body of a Scythian, like those who Aristotle said had no intoxication and therefore no flute players, to the body of an Indian, like those Pyrrho met while traveling with Alexander before coming home a skeptic, and says that Greeks and Indians enjoy different things.  Some people enjoy beef more than fish, others get sick from Lesbian wine (from Lesbos, like Sappho).  Legend has it that an old woman who lived near Athens could consume hemlock without harm (clearly different from Socrates).  Some individuals are immune to common poisons, others are allergic to common goods.  Sextus says that, if our bodies differ so, and if the body is an image of the soul, it is likely that our souls differ as well.  Modern psychology confirms this today, as we do share a generally similar mind to all of humanity while varying individually, sometimes in profound ways.

boat india river

Old people are affected by temperature more than young people, but young people are affected by color and sound more than old people, showing that in some ways the old are more sensitive to perceptions while in others the young.  Lamps which seem bright at night are dim in the daytime.  When in motion (such as on a boat), things that are standing still appear to be in motion, but from far away, things (such as boats) that are in motion seem to stand still.  Things which we feel are shameful when sober are enjoyable when drunk.  The same wine seems sour after dates or figs, sweet after nuts or beans.  People are cold after exiting the warm public bath house, but they were not cold before they entered.  The conditions of a particular situation affect the perception of the situation.

Greek lyre player

While dogmatists argue about what is universal and common to all, arguing that Plato or Epicurus is exclusively right, Sextus says that poets and playwrights have a better understanding, knowing all too well the tragedy that follows from various feelings and convictions.  The dogmatists, claiming to exclusively know the truth, are themselves part of a dispute, evidence that one must take a position on a matter to see things a certain way.  The various dogmatic schools, opposed to each other as well as to skepticism, show that dogmatism is insufficient for investigating truth.

Zeno of Citium

Similar to the Eleatic infinite regress of place in Zeno and form in Plato’s Parmenides, Sextus argues that if we want to prove what we think is exclusively true, we then would have to prove that our proof is true, and then prove that this proof is true, resulting in a similar infinite regress.  Sextus repeats several times, “Everything, therefore, is relative”.  While dogmatists argue that some things are the best, others are the worst, that some things are clear, and others unclear, that some things are equal, and other things are unequal, that some things are similar, and other things are dissimilar, all these are relative, not absolute or exclusive.

cloud lightning

Speaking about the rare being striking while the same when common is normal, the ninth trope of Aenesidemus, Sextus argues that comets, earthquakes and lightning are considered important and meaningful because they are rare, while the sun, which is far brighter, is not striking because it rises everyday.  Similarly, one who sees the sea for the first time finds it astonishing.  This itself is strikingly similar to the Chinese Daoist Zhuangzi, who says that a well frog would consider the ocean a ridiculous fantasy.  Sextus also says that the human body would be astonishingly beautiful to us if we did not see it often, that water would be expensive if it was rare, and gold would be cheap if it was a common stone.

Socrates and students Islamic

Sextus says that recent skeptics, presumably those between Aenesidemus and himself, gave five modes different from the ten tropes for aiding in the suspension of judgement, and he explains each and discusses types of reasoning that each is useful against.  First, there is dispute, that matters are disputed among the common people and the wisest of philosophers alike.  Second, there is ‘ad infinitum’, infinite regress such as those employed by the Eleatics, that any argument would require an additional argument to confirm the argument, and any source would require an additional source to confirm the source.  Third, there is relativity, that anything good is only so good, anything far is only so far.  Fourth, there is the hypothetical, identical to the ‘sayadvada’ principle of the Indian Jains, that all beliefs are put forward hypothetically without absolute confirmation, impossible given the second mode of ‘ad infinitum’.  Fifth and finally, there is the reciprocal, that any belief supported about a thing requires the thing to support the belief, resulting in circular reasoning.


The skeptical philosopher of science Feyerabend, who argued as a “theoretical anarchist” that there is no particular scientific method, wrote that many believe circular reasoning is wrong, but in fact it is one of the most dominant forms of thought on the planet, and often it works just fine.  Our assumptions, that the sun will rise tomorrow or our culture is good, are circular circuits of thought that are normally undisturbed.  We believe that the sun will rise because the sun has risen again and again.  It is fine to believe this, and then see the belief confirmed again and again, but it is not proven that the sun will rise tomorrow, and if the earth was obliterated by a solar flare, the sun would cease to rise above the turning horizon.

Circle & Line

Sextus says that these five modes, which presumably are an attempt to boil down the ten tropes of Aenesidemus, were further boiled down to two modes by the same unnamed “recent skeptics”.  These two are essentially the second and fifth modes of the previous five.  Things must either be known in themselves, or known via something else.  If things are known in themselves, it results in circular reasoning.  If things are known in something other than themselves, it results in infinite regress.  Things can be relatively known in themselves and via other things (such as the forms of Plato), but they cannot be known absolutely without escaping the dual problem of circular reasoning and infinite regress.

heraclitus bust

Sextus ends the first book of his Outline by distinguishing skepticism from several other similar philosophies, first and foremost that of Heraclitus, who does make dogmatic assertions (for instance, that all is made of fire and one thunderbolt strikes through the root of everything).  Sextus admits that Aenesidemus and his followers believed that skepticism is a path to Heracliteanism, seeing everything as made of relative oppositions, but Sextus believes that Aenesidemus was wrong because Heraclitus is not entirely skeptical, advancing dogmas of his own.  Sextus argues the same of Democritus, who asserted the truth of atomism while also being decently skeptical.  Being a fan of skepticism myself, it is often the case that skeptics accuse each other and dogmatists of being dogmatic, while dogmatists often accuse each other and skeptics of not possessing the right dogma.

Skepticism after Sextus

Byzantium Empire Map

Much of Sextus’ work survived in Byzantium (ancient Ionia, modern day Turkey), where the Roman Empire had moved its capital before its collapse to get closer to the rich trade between the Middle East and East Asia along the silk road.  After Byzantium became Islamic, and then the Ottoman Empire, Sextus’ works were brought to Renaissance Italy in 1427 CE by Francesco Filelfo, where they were translated into Latin and studied.

Life of Martin Luther

In response to the Protestant Reformation, the rise of Rationalism and the success of the natural sciences in Europe that challenged earlier cosmology, aided by Islamic algebra and technology, the Catholic Church used Pyrrhonian Skepticism to argue that mortal humanity is incapable of absolute knowledge.  While the Catholic Church was a central source of scholarship and knowledge of Medieval Europe, Protestants have long identified their reformation with reason and science, enabling humanity to free itself of the institution of the Church.  Catholic theologians argued that, according to the arguments of Pyrrho and Sextus, Protestant reformers could not justify their beliefs, ignoring the minor inconvenience that skepticism denies everyone, including Catholic theologians, of absolute justification equally.


Not all Catholic theologians and philosophers agreed with Pyrrhonian Skepticism.  Rene Descartes, mentioned with Plato’s cave in the Republic, often considered the first modern European philosopher, was a French Catholic thinker who argued that skepticism was self-defeating, famously writing, “I think, therefore I am”.  If we can be certain we exist, Descartes argued, then we cannot be entirely skeptical, and we can have faith that truths that appear consistent (such as 2 plus 3 always equaling 5) are certain.  As mentioned with Plato, Descartes was also arguing against the position of Gnostic heretics who still lived in remote parts of the French countryside, whose beliefs opposed those of the Catholic Church.  Against Pyrrhonian skeptics and Gnostics, Descartes argued, in conformity with the teachings of the Catholic Church, that the world is not ruled by a deceiving demon but by a kind and loving God who has given us certainties in our world which we can know through the rational pursuits of science and mathematics.  In a letter to a priest named Bourdin, Descartes argued that skepticism was unfortunately quite alive, and that he was the first to successfully argue against skeptics.

Hume Grey

Against Descartes, David Hume, the Scottish skeptical Empiricist, argued that Pyrrho was indeed right about truth and the human mind, but our attachments and prejudices are too strong for us to be genuine skeptics.  Unlike Rationalists, whose tradition begins with Descartes and who argue that absolute truth and certainty can be achieved through the use of reason, Empiricists, whose tradition begins with Hume argue that ‘truth’ is always prejudice and assumption, useful to us in preserving our lives and pursuing our interests but impossible to completely confirm with absolute certainty.  Hume wrote in his central work, “Philosophy would render us entirely Pyrrhoian were not nature too strong for it”.  Like Pyrrho and other skeptical inquirers, Hume argued that all truths are known inductively or empirically (from which the Empiricists get their name), perceived in each instance as similar but never known absolutely, which required continuous scientific inquiry into truth.  While, unlike the Rationalists, Hume did not believe that reason can help us deduce absolute truth, we should continue to investigate everything with reason and science, as we can never know absolute truth.


For Hegel, the German Idealist and Phenomenologist, Descartes and Rationalism were the first great dogmatic movement in modern European philosophy, and Hume and Empiricism were the first great skeptical movement in response, just as Hegel saw Aristotle as the great dogmatist and Heraclitus as the great skeptic of ancient Greek philosophy.


Hume, and through him Pyrrho, influenced many skeptical thinkers of modern Europe, including Nietzsche, who saw himself as a modern German Heraclitus.  Nietzsche argued that we are easily sheep, sleepers as Heraclitus put it, and that we should think critically as individuals about everything that religion, politics and science tells us to believe.