Profiles in skepticism: Sextus Empiricus

The enigmatic philosopher who inspired millennia of debate

The mysterious Sextus Empiricus, image from Wikimedia.

Ancient skepticism was the root of a long tradition of critical thinking that eventually led to the maturing thought of Medieval, Renaissance, and finally modern and contemporary authors, ranging from John of Salisbury (1110-1180) to Michel de Montaigne (1533-1592), from René Descartes (1596-1650) to Baruch Spinoza (1632-1677), from David Hume (1711-1776) to Friedrich Nietzsche (1844-1900), and so on.

In this six-part series, of which the present is the last entry, we have looked at only some of the major figures belonging to the two major strands of ancient skepticism: Pyrrhonism and Academic Skepticism. We have discussed the Cyrenaics, Pyrrho, Arcesilaus, Carneades, and Cicero, though we have skipped Timon, Aenesidemus, Philo of Larissa, the medical empiricists, and Plutarch. Let me conclude with a look at one of the most influential and controversial of the Pyrrhonists: Sextus Empiricus. (Much of this discussion is based on chapter 10 of Skepticism: From Antiquity to the Present, edited by Diego Machuca and Baron Reed, Bloomsbury Academic, 2015, entry authored by Tad Brennan and Cliff Roberts.)

Sextus is crucial in the history of skepticism because he is the one that made it possible for the approach to be transmitted to the Renaissance, and hence to modernity. Unfortunately, we know next to little about Sextus himself. He lived a century before or after the year 200 CE, somewhere in a major city in the Mediterranean area. Is that vague enough for ya?

He was clearly influenced by Aenesidemus, a 1st century BCE Pyrrhonist who introduced the famous “ten modes” (more on them below) and, arguably, the notion of suspension of judgment. Aenesidemus was likely a member of the Platonic Academy, and a contemporary of Philo of Larissa and Cicero.

In part because of his name, Empiricus, Sextus is thought to have been a doctor affiliated with the empiricist school of the time, though he actually states his own preference for the alternative, so-called methodical school. Moreover, Sextus himself tells us that he wrote treatises on medicine, which have not survived. Three of Sextus’s works do survive: Outlines of Pyrrhonism, Against the Professors in six chapters, and another Against the Professors in five chapters.

According to Sextus a skeptic is someone who is capable, given any controversial topic, to come up with equally compelling arguments pro and against. Since he realizes that he cannot assent to both arguments (because they are contradictory) the skeptic therefore suspends judgment (epokhē). This in turns, we are told, leads to tranquillity of mind (ataraxia), which is the goal of Pyrrhonist philosophy.

Sextus states that suspension of judgment is not contradictory to giving assent to certain “evident” matters, based on “what is apparent.” There is much controversy even today about what exactly counts as evident vs non-evident matters in Pyrrhonism. Brennan and Roberts say that for decades now the scholarly debate about how to interpret Sextus has been dominated by two contributors: Michael Frede and Myles Burnyeat. Frede is sympathetic to Sextus, while Burnyeat is more critical.

Let’s start with Frede. He points out that Sextus claims to believe a number of things and only to suspend judgment on non-evident matters. The category of evident matters is taken by Frede to be very inclusive, so that the Pyrrhonist goes about his day like most of us, believing all sorts of things. He only engages in epokhē concerning the sort of issues that the so-called dogmatist philosophers disagree about: Platonic forms, atoms, whether virtue is the chief good, and so on.

From this description it may appear that Sextus believes in evident things, like chairs, but not in non-evident things, like the Form of the Chair. Seen this way, Pyrrhonian skepticism turns out to be about the content of beliefs. But Frede maintains that that’s clearly not what Sextus meant, because sometimes he attacks beliefs that at other times he accepts. It seems, therefore, that it isn’t the content of a belief that is problematic, but rather the dogmatic attitude one has about a certain belief:

“Dogmatic beliefs claim to contain deeper insights into the true nature of things. … It is characteristic of the dogmatists that they believe it is possible to go behind the surface phenomena to the essence of things, to the nature of things, to true reality.” (Frede 1979: 179, 187, cited in Brennan and Roberts)

This way of putting it makes Pyrrhonism anticipate a momentous modern debate in ontology and epistemology, featuring giants of the caliber of David Hume and Immanuel Kant. Hume had mounted a formidable, skeptical, attack on the whole of metaphysics, particularly on the concept of causality. Kant wanted to salvage metaphysics, and famously wrote:

“I freely admit that it was the remembrance of David Hume which, many years ago, first interrupted my dogmatic slumber and gave my investigations in the field of speculative philosophy a completely different direction.” (Prolegomena to Any Future Metaphysics, 4, 260; 1783)

Interestingly, Kant frames the debate as one of skepticism (Hume) vs dogmatism, apparently unconcerned of counting himself as allied with the latter approach. In modern terms, we can understand Kant’s response to Hume as a rebuttal of empiricism, the very word we find embedded in Sextus’s name! Specifically, Kant separates the realm of existence into two components: noumena and phenomena. Noumena refers to how the world actually is, a realm that is unaccessible by human mental faculties. Phenomena is what we perceive and react to, presumably a reflection (in some unknown way) of the noumena. It is only phenomena that are the subject of human inquiry and science.

The debate can also be cast in terms of contemporary philosophy of science, where dogmatists are so-called realists about the sort of entities described by science, like electrons, quarks, and so forth. By contrast, skeptics would then be anti-realists, arguing that we don’t have access to the intrinsic nature of electrons and quarks, and the only thing we can do is to describe phenomena. The discussion initiated by Sextus, then, strikes at the very heart of what we think science is in the business of doing: anti-realists say that scientists simply produce empirically adequate models of phenomena, period. Realists say that scientists are after the ultimate reality that produces such phenomena. It is worth mentioning that—for all the influence of Kant on modern thought—most scientists and philosophers of science are realists.

Back to the ancient debate:

“The Dogmatists [according to Sextus] are figures whose searching has terminated, because they claim to have discovered the truth. [However,] it is clear to us as sensitive readers of, e.g., Plato that this misrepresents his attitude toward many of his own doctrines; his own searching was by no means at an end when he wrote his dialogues. But Sextus clearly characterizes Plato and other Dogmatists as people who believe that their answers have put an end to searching.” (Brennan and Roberts)

So Sextus may have been a bit unfair to the people he called dogmatists, which included any philosopher who was not a Pyrrhonist. That said, the situation is a bit complicated. The Stoics, for instance, did claim that their famous sage was capable of giving final assent to certain impressions, and that such assent was “stable,” that is, it couldn’t be overturned by further evidence or argument. Then again, the Stoics also agreed that most people are not sages, and that they do not therefore have a firm grasp of the truth. My opinion is that the skeptics (both Pyrrhonists and Academics) were right even about the sage: not even a perfectly reasoning human being (whatever that means) can arrive at conclusions that are incapable in principle of being overthrown.

Let us now take a look at Burnyeat’s, ahem, skepticism about Pyrrhonism. He is critical of the approach on two main grounds: first, if the Pyrrhonist life were possible, he argues, it would be horrible and sub-human. Second, Pyrrhonism is at any rate not possible because the philosophy is incoherent, since it claims not to rely on belief, and yet its elements—from opposing arguments to suspension of judgment—all require explanations in terms of belief.

Burnyeat points out that Sextus says that he believes only in appearances. But appearances do not admit of truth values (i.e., they are not true or false), and so one’s attitude toward appearances cannot be a belief. For instance, the Pyrrhonist cannot coherently say that he believes two arguments to be equipollent (of the same validity and soundness), at best he can say that they appear to be equipollent:

“This appearance, so called, being the effect of argument, is only to be made sense of in terms of reason, belief, and truth—the very notions the skeptic is most anxious to avoid. … [No tranquility can be produced by suspension unless the Skeptic is] in some sense satisfied … that no answers are forthcoming, that contrary claims are indeed equal. … How can Sextus then deny that this is something he believes?” (Burnyeat 1980: 52, cited in Brennan and Roberts)

Burnyeat makes an interesting point in response to Frede: Pyrrhonism might work if the Pyrrhonist were to somehow insulate ordinary from philosophical beliefs. For instance, I may disbelieve the notion of the passage of time (which is what acceptance of Einstein’s general relativity requires) while at the same time telling my friend that I’ll be “on time” at our appointment for an aperitivo at our favorite bar. The problem, Burnyeat says, is that no skeptic ever claimed to be insulating concepts in this fashion, which means that the skeptic could not at the same time state to believe in the passing of time and yet to suspend judgment about it.

Regardless of what we may think of the desirability and coherence of Pyrrhonism, arguably the major contributions of the philosophy to the world have been the famous “modes,” which were originally meant as techniques to build equipollence between different arguments, thus leading to suspension of judgment and ultimately ataraxia.

There are two groups of such modes, the ten attributed to Aenesidemus and the five attributed to Agrippa, a first century CE Pyrrhonist. The ten modes are all variants of one underlying strategy: if people disagree about something, or if the same thing appears to be different under different circumstances, suspension of judgment is warranted. Here are the ten modes in full splendor:

(1) Different animals have different impressions;

(2) Different people have different impressions;

(3) Even for the same person, sense data are sometimes contradictory;

(4) Sense data vary with changes in circumstances;

(5) Sense-data vary according to local relations;

(6) Objects are known only indirectly through the medium of air, water, etc;

(7) Objects change color, temperature, size, and motion depending on the circumstances;

(8) Perceptions are relative and interact with each other;

(9) Our impressions become less strong by repetition and custom;

(10) People are brought up with different beliefs, under different laws and social conditions.

These, by contrast, are the five modes of Agrippa:

(i) Dissent, when people disagree on whether something is true or not;

(ii) Infinite regress, when one explanation is followed by another, and another, and so on;

(iii) Relativity, when different observers perceive what is allegedly the same object differently;

(iv) Dogmatic hypothesis, when at some point an axiom or assumption is introduced;

(v) Circularity, when something to be explained reappears later on as providing the explanation.

Notice that Agrippa’s modes (i) and (iii) essentially recapitulate the ten modes of Aenesidemus, so that we can simply use Agrippa’s version. As I pointed out in another essay, the subset of Agrippa’s modes (ii), (iv), and (v) are nowadays known as Agrippa’s (or Münchhausen’s) trilemma, and are thought to represent a definitive argument against the possibility of certain knowledge. Which is ironic, given that Sextus would consider such a conclusion an example of dogmatism.

[Previous installments in this series: The Cyrenaics; Pyrrho; Arcesilaus; Carneades; Cicero.]