Protagoras from Lives of the Eminent Philosophers
Diogenes Laërtius
About Protagoras
In this excerpt from Lives of the Eminent Philosophers, Diogenes Laërtius introduces us to Protagoras (c. 490–420 BCE), one of the most famous and controversial figures of early Greek philosophy. Unlike earlier philosophers who explored the nature of the cosmos or metaphysical truths, Protagoras turned his attention to human beings—how we live, argue, learn, and decide what’s right or wrong.
Protagoras was a Sophist, which means he was part of a group of intellectuals who taught rhetoric, debate, and practical reasoning—for a fee. Sophists weren’t always well-loved by traditional philosophers (especially Plato), since they were often more focused on persuasion than truth. But that’s part of what makes Protagoras so important: he represents a shift in Greek thought from nature (physis) to culture (nomos), from the objective world to the world of human experience.
His most famous claim is: “Man is the measure of all things.” This bold declaration is a classic expression of relativism—the idea that truth, especially in matters of knowledge and ethics, depends on the individual or the society. What’s true for you might not be true for me. Protagoras wasn’t saying “anything goes,” but he was challenging the idea that there is a single, objective truth accessible to all.
According to Diogenes, Protagoras was also a skilled and influential teacher who may have advised Pericles and other major Athenian leaders. He wrote several works (mostly lost), including Truth, where he laid out his relativistic philosophy, and another on the gods in which he claimed, “Concerning the gods, I can know nothing”—earning him charges of impiety.
Despite the controversy (or maybe because of it), Protagoras had a huge impact on the development of rhetoric, ethics, education, and the role of critical thinking in public life. Even Plato, who sharply criticized the Sophists, gave Protagoras a central role in one of his dialogues, depicting him as a worthy sparring partner for Socrates.
In the long run, Protagoras’ influence helped shape Western ideas about subjectivity, tolerance, pluralism, and the value of persuasive speech in democratic societies. He might not have believed in absolute truth, but his ideas continue to spark serious philosophical debates even today.
Before You Read
As you read about Protagoras, keep in mind that his views push against the idea that there’s a single, universal truth. He challenges us to think about how context, perspective, and culture shape what we take to be real or right.
Ask yourself: Do you think truth is the same for everyone? Or does it depend on how someone sees the world? What about moral truths—can they vary from person to person or society to society? And how do we know when someone is genuinely wise versus just really good at arguing?
Also think about the role of education and persuasion. Protagoras believed that teaching people how to argue well was a civic good. Plato worried that this could be manipulative. Who’s right? Or are both views worth considering?
Guiding Questions
- What does Protagoras mean when he says, “Man is the measure of all things”?
- How does Protagoras’ relativism challenge traditional views of truth and morality?
- Why was Protagoras charged with impiety, and what does this reveal about Athenian society?
- How do Sophists like Protagoras compare with philosophers like Socrates?
Protagoras from the Lives of the Eminent Philosophers
Protagoras, son of Artemon or, according to Apollodorus and Dinon in the fifth book of his History of Persia, of Maeandrius, was born at Abdera (so says Heraclides of Pontus in his treatise On Laws, and also that he made laws for Thurii) or, according to Eupolis in his Flatterers, at Teos; for the latter says:
Inside we’ve got Protagoras of Teos.
He and Prodicus of Ceos gave public readings for which fees were charged, and Plato in the Protagoras[69] calls Prodicus deep-voiced. Protagoras studied under Democritus. The latter[70] was nicknamed “Wisdom,” according to Favorinus in his Miscellaneous History.
51. Protagoras was the first to maintain that there are two sides to every question, opposed to each other, and he even argued in this fashion, being the first to do so. Furthermore he began a work thus: “Man is the measure of all things, of things that are that they are, and of things that are not that they are not.” He used to say that soul was nothing apart from the senses, as we learn from Plato in the Theaetetus,[71] and that everything is true. In another work he began thus: “As to the gods, I have no means of knowing either that they exist or that they do not exist. For many are the obstacles that impede knowledge, both the obscurity of the question and the shortness of human life.” 52. For this introduction to his book the Athenians expelled him; and they burnt his works in the market-place, after sending round a herald to collect them from all who had copies in their possession.
He was the first to exact a fee of a hundred minae and the first to distinguish the tenses of verbs, to emphasize the importance of seizing the right moment, to institute contests in debating, and to teach rival pleaders the tricks of their trade. Furthermore, in his dialectic he neglected the meaning in favour of verbal quibbling, and he was the father of the whole tribe of eristical disputants now so much in evidence; insomuch that Timon[72] too speaks of him as[73]
Protagoras, all mankind’s epitome,
Cunning, I trow, to war with words.
53. He too first introduced the method of discussion which is called Socratic. Again, as we learn from Plato in the Euthydemus,[74] he was the first to use in discussion the argument of Antisthenes which strives to prove that contradiction is impossible, and the first to point out how to attack and refute any proposition laid down: so Artemidorus the dialectician in his treatise In Reply to Chrysippus. He too invented the shoulder-pad on which porters carry their burdens, so we are told by Aristotle in his treatise On Education; for he himself had been a porter, says Epicurus somewhere.[75] This was how he was taken up by Democritus, who saw how skilfully his bundles of wood were tied. He was the first to mark off the parts of discourse into four, namely, wish, question, answer, command;[76] 54. others divide into seven parts, narration, question, answer, command, rehearsal, wish, summoning; these he called the basic forms of speech. Alcidamas made discourse fourfold, affirmation, negation, question, address.
The first of his books he read in public was that On the Gods, the introduction to which we quoted above; he read it at Athens in Euripides’ house, or, as some say, in Megaclides’; others again make the place the Lyceum and the reader his disciple Archagoras, Theodotus’s son, who gave him the benefit of his voice. His accuser was Pythodorus, son of Polyzelus, one of the four hundred; Aristotle, however, says it was Euathlus.
55. The works of his which survive are these:
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- The Art of Controversy.
- Of Wrestling.
- On Mathematics.
- Of the State.
- Of Ambition.
- Of Virtues.
- Of the Ancient Order of Things.
- On the Dwellers in Hades.
- Of the Misdeeds of Mankind.
- A Book of Precepts.
- Of Forensic Speech for a Fee, two books of opposing arguments.
This is the list of his works.[77] Moreover there is a dialogue which Plato wrote upon him.
Philochorus says that, when he was on a voyage to Sicily, his ship went down, and that Euripides hints at this in his Ixion. According to some his death occurred, when he was on a journey, at nearly ninety years of age, 56. though Apollodorus makes his age seventy, assigns forty years for his career as a sophist, and puts his floruit in the 84th Olympiad.[78]
There is an epigram of my own on him as follows:[79]
Protagoras, I hear it told of thee
Thou died’st in eld when Athens thou didst flee;
Cecrops’ town chose to banish thee; but though
Thou ’scap’dst Athene, not so Hell below.
The story is told that once, when he asked Euathlus his disciple for his fee, the latter replied, “But I have not won a case yet.” “Nay,” said Protagoras, “if I win this case against you I must have the fee, for winning it; if you win, I must have it, because you win it.”
There was another Protagoras, an astronomer, for whom Euphorion wrote a dirge; and a third who was a Stoic philosopher.
About this reading
Robert Drew Hicks translation of Protagoras was retrieved from Wikisource . This work is in the Public Domain.
