BMCR 2005.09.66

Epistemology after Protagoras. Responses to Relativism in Plato, Aristotle, and Democritus

, Epistemology after Protagoras : responses to relativism in Plato, Aristotle, and Democritus. Oxford: Clarendon Press, 2005. x, 291 pages ; 24 cm. ISBN 0199262225 $74.00.

The study of ancient skepticism usually begins with the works of Sextus Empiricus. But Sextus understood perfectly well that the possibility and cogency of skeptical thinking lay at the heart of the enterprise of philosophy itself as the Greeks conceived of it some 700 years before. Start with the hypothesis that nature ( phusis) is a kosmos, that is, it has some sort of unified structure or arrangement that is amenable to understanding. This hypothesis immediately forces us to acknowledge that over against ordinary thinking according to which things appear as they do because they are that way, in fact things must be different from the way they appear. The contrast between appearance and reality at once locates the path of philosophy — trying to gain knowledge of the reality behind appearances — and the alternative path of skepticism, denying that any such knowledge is possible.

Mi-Kyoung Lee’s new monograph aims to explore skepticism in ancient Greek philosophy before the Skeptics. In particular, she proposes for analysis the skeptical tendencies in the philosophical position of Protagoras and the responses to these in Democritus, Plato, and Aristotle. Much of this is well-trodden ground, although with respect to Democritus, more careful attention is here paid than is typical, and to very good effect. Lee’s thesis is that in the “classical period,” “skepticism was in the air — not in the form of a well-defined school of thought or position, but in the form of certain loosely related ideas and arguments” (1). It was Protagoras (ca. 485-415 BCE) who initially threatened the innocent presumptions of the Greek philosophers in his dramatic declaration that “man is the measure of all things, of what is that it is, and of what is not that it is not.” He did this in a book provocatively titled Truth, and thus challenged his predecessors to abandon the pretension that wisdom was the discovery of what was really “out there,” that the “measure” of all that is and is not is nature itself.

After setting out her thesis, in the second chapter Lee takes up the difficult task of determining the contents of Protagoras’ lost work Truth. In fact, we possess only one or two sentences of that work, the statement of the “measure” doctrine, much quoted in antiquity. The measure doctrine is an expression of a sort of relativism; it is not necessarily an expression of skepticism. Indeed, if Truth did aim to do nothing more than argue for a relativistic criterion of truth, the soi-disants skeptics would have classified Protagoras as a dogmatist (cf. Sextus Empiricus, Outlines of Pyrrhonism, I.216). What was needed to turn relativism into skepticism was a supplementary argument for the denial of any knowledge about how the world was independent of how it appeared to us, for this would compromise the view that the way the world appeared to us was the truth. Protagoras’ work would actually be in this way an ironic rejection of truth with a capital “T” and a trivialization of it via its relativization. Sextus, following Plato in Theaetetus, thought that Protagoras actually had or was in fact committed to a doctrine of metaphysical flux, the so-called “secret doctrine” which was supposed to explain how truth arises in our contact with the sensible world. Lee argues, reasonably enough, that Protagoras probably did not embrace such a doctrine (23-9). This leaves the question — explored in later chapters — of what exactly Plato’s point was in saddling the Protagorean measure doctrine with such heavy metaphysical baggage.

The third chapter of the book tries to explain Plato’s way of treating the measure doctrine. Lee argues that Plato attributes to Protagoras both relativism about truth and what she terms “infallibilism,” the view that persons are infallible judges of the way the world is (31). These two positions, however, are potentially in some tension: being an infallible judge of the way things are is not equivalent to being a measure of the way things appear to one, that is, to truth as relative. Lee maintains that infallibilism is the key concept in Plato’s understanding of the measure doctrine and that, in fact, there is no evidence that Protagoras was actually a relativist about truth. But she argues that infallibilism does not account for the relativism that Plato does attribute to Protagoras. By this she means that “p is true for A” is equivalent to “A believes p.” In effect, what Protagoras was probably trying to say (despite Plato’s use of him) was that there is no difference between truth and appearance. Hence, Protagoras becomes the ironic skeptic alluded to above, not the hardcore relativist about truth. The latter position arises only when one begins to reflect on “the relativism of fact” or the claim that appearances are facts that are always relative to someone.

In the fourth chapter, Lee sets out the reasons why both Plato and Aristotle held that the relativism of fact entails an unsustainable relativism about truth. The famous argument employed by Plato against Protagoras concerns the status of so-called second-order beliefs, e.g., Socrates’ belief that Theaetetus’ belief is false. If Protagoras insists on his measure doctrine, he will maintain that Socrates’ belief is true for Socrates as Theaetetus’ belief is true for him. But this is not a case like ordinary first-order beliefs, for here Socrates’ belief is in the falsehood of Theaetetus’ belief, not a belief that “such-and-such is as it appears to me.” Either Socrates’ belief must be false or Theaetetus’ belief must be false (as Socrates maintains). In either case, there is a false belief. This is not a problem for a relativist about truth, one who maintains that “what is true for me might well be false for you.” But it is a problem for the infallibilist who maintains that everyone is his own infallible measure of the truth. If Protagoras insists that the measure doctrine is not true for those who claim it to be false, he has ceded his position that everyone is an infallible measure of the truth (54). In short, the measure doctrine cannot be objectively true, that is, true whether or not anyone believes it to be true.

Protagoras is not without resources to reply to this sort of argument, as Lee shows. Most important, he can simply embrace the relativity of truth, thereby abandoning infallibilism. In that case, what would be needed to defeat Protagoras would be an argument against the relativity of truth, which is exactly what Plato provides in Theaetetus 184-186.

According to Aristotle in Metaphysics Book 4, the relativity of truth does not rescue Protagoras, for this embrace entails a denial of the principle of non-contradiction. Thus, if Socrates believes that Theaetetus’ belief that the wind is hot is false (a belief that is true for Theaetetus), then Protagoras must maintain that there are some beliefs that are both true and false (i.e., the belief that the wind is hot for Theaetetus). Protagoras could, if he likes, insist that there is no contradiction because Socrates’ belief is just true for him; Protagoras’ belief is just true for him, and these are different beliefs. But Aristotle replies that adding “for S” to “true” is empty verbiage, maintained only for the sake of argument. Thus, someone who added “for me” to “it is true that p” would be adding no content even if “p” were to stand for “the wind is cold for me.”

In the fifth chapter, Lee focuses on Theaetetus and its “secret doctrine” supposed by Plato to provide for Protagoras the strongest possible metaphysical basis for his theory. At the beginning of the dialogue, Theaetetus offers a definition of knowledge as perception. This definition is associated by Socrates with Protagoras’ claim that whatever appears to be the case for one is the case for one. The connection between the definition and the claim is not perspicuous. Lee argues that the latter is supposed by Plato to be a clarification of the definition (79). This apparently means that one committed to the definition will also be committed to the claim. The claim, in turn, if it is to be made good generally, must be supported by something like the secret doctrine. This is a loose collection of theses, the center piece of which is the Heraclitean idea that everything is in constant flux, along with the supplementary ideas of the relativity of all being, that is, that everything is only insofar as it comes to be for someone. As Lee rightly notes, the secret doctrine is, thus described, more than merely a doctrine of Heraclitus. She argues that in fact Protagoras’ measure doctrine neither implies nor is implied by the secret doctrine. Rather, the dialectic works in this way: “if Protagoras’ thesis and the secret doctrine are true, then Theaetetus’ definition comes out true as well (91).” According to Lee, the Theaetetus’ rejection of the secret doctrine as inconsistent is not meant to refute Protagoras but rather to remove but one fairly popular support for his doctrine (113).

Chapters six and seven provide a close examination of Aristotle’s Metaphysics Book 4, chapter 5. Lee shows here how closely Aristotle is following the examination of Protagoras in Theaetetus. Like Plato, Aristotle associates Protagoras’ measure doctrine with a doctrine of flux; in addition, he connects both doctrines with a doctrine that the principle of non-contradiction, as understood by Aristotle, is false. These three doctrines, taken together, entail skepticism, that is, the claim that the knowledge of the truth is impossible. Lee argues that Aristotle proposes to deal with this skeptical claim by showing that commitment to the positions of Protagoras or Heraclitus or to the denial of the principle of non-contradiction all rest upon an assumption that only what is perceptible is real (131-2). Remove this assumption, and the entire skeptical edifice crumbles.

Aristotle himself in De Anima acknowledges the similarities of perception, on the one hand, and thinking and knowing, on the other, though he is careful to resist identifying them. Lee provides a careful survey of how Aristotle treats his predecessors in this regard, showing where they failed to see the differences between perception and higher cognition. Underlying their mistaken accounts is the principle that like cognizes like. As this principle is employed by the Presocratics, perception is a type of alteration occurring when a perceptible of some kind causes a perceptual state that is like the perceptible itself, say, when something hot causes us to feel hot. Whatever plausibility this has in an account of perception, when applied to thinking, it does not, among other things, allow for the possibility of error (159). These philosophers wrongly assimilated a (higher) cognitional state and what it is about to a perceptual state and its cause. Accordingly, those who tend to hold that thinking is a form of perception suppose that only what is perceptible is real, presumably, on the further perception that the real is somehow cognizable by us, that is, that the real is intelligible.

Chapters eight and nine, the most original part of the book, focus on Democritus (ca. 460 to between 390 and 350 BCE) whose stature among his contemporaries is belied by the dearth of evidence remaining and by Plato’s surprising lack of attention to him. Lee here mines the extant testimonies — especially Aristotle, Theophrastus, Sextus Empiricus, and Galen — to show that Democritus was a “modified Protagorean because he rejects the thesis that all beliefs are true, but accepts the idea that things are for each as one’s senses tell them.” Lee argues that Democritus rejected Protagoras’ measure doctrine, denying relativism about truth (188-9). Yet Democritus was a relativist about perception and sensible qualities. We cannot go wrong about what we perceive because our perception is the effect of atoms acting on us. There is, then, a divide between what we perceive and the way the world really is, meaning that we can never know how things are in themselves. Hence, one might surmise that there is a skeptical tendency in Democritus, and indeed, some of his fragments can be read this way. Yet, Sextus resisted — and Lee maintains that he was right to resist — the recruitment of Democritus into the ranks of the skeptics, for he also held that the senses are an indispensable means to knowledge about what is non-evident. Somewhere between the senses being sufficient for knowledge of the truth and their being necessary though not sufficient is the skeptic/empiricist terrain occupied by Democritus. What sets Democritus apart from the Academic Skeptics, at any rate, is that he believed that knowledge was possible (220); what sets him apart from the empiricists is his conviction that knowledge is primarily if not exclusively of the non-evident.

The principal strength of this fine book is the meticulous reconstruction of the epistemological views of Protagoras and Democritus. The principal weakness of the book is owing to the fact that Lee is also or especially concerned to explore the engagement with Protagoras and Democritus by Plato and Aristotle. Not unreasonably, she does this based on the hypothesis that an undercurrent of skepticism was to be found among the ideas of the two Presocratic giants. The problem with this is that both Plato and Aristotle criticize their predecessors based on their own firm views about what knowledge is and their convictions that the Protagorean and Democritean approaches cannot attain it. Plato holds that knowledge is exclusively of separate, intelligible reality; Aristotle holds that knowledge is exclusively of what “cannot be otherwise.” How these two views are related is another story. But the criticism of Protagoras and Democritus — which is what this book is to a significant extent about — comes from these perspectives.

Lee does not say much about the views of knowledge that generate the criticism. Admittedly, a thorough exposition of these is the subject of one (or more) additional books. Yet without a more explicit discussion of these views, the criticism of the skeptical tendencies in Protagoras and Democritus is rather captious. One way to defeat a skeptic or to disarm her is to agree that there is such a thing as knowledge and to insist that the word “knowledge” is merely to be applied stipulatively according to whatever socially rooted criteria happen to be convenient. To be a skeptic about knowledge thus construed would indeed be foolish. This way of dissolving the skeptical challenge has always been attractive to some philosophers. But it is not the way followed by Plato or Aristotle. Lee’s book would have been even better if she had taken seriously Sextus’ remark to the effect that if skepticism can be made to prevail, then Greek pretensions to wisdom will be unmasked for what they are. Plato and Aristotle took skepticism as seriously as did Sextus and for exactly the same reasons.