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Summary Article: Protagoras
from The Encyclopedia of Ancient History

Protagoras of Abdera (ca. 490–420 BCE), Greek intellectual, pupil of Democritus, author of treatises on grammar, logic, Ethics, and politics, was involved in Athenian life during a period of intensive intellectual creativity. He was appointed lawgiver in the Panhellenic colony of Thourioi but charged with impiety (Asebeia) upon his return to Athens and forced to flee — according to a not entirely reliable source. Protagoras figured in Eupolis' play Flatterers (PCG frs. 157, 158 Kassel–Austin). He is believed to have died in a shipwreck.

Protagoras enjoyed a universally distinguished reputation for his philosophical wisdom (Pl. Menex. 91e), but also aroused opposition as a "Sophist" (Pl. Prt. 317b; see Sophists, Greece). He was criticized for cultivating political shrewdness; for teaching aspiring politicians how to persuade multitudes and how to acquire dominion over others, and for receiving payment for this activity; for adopting a skeptical attitude towards the possibility of certain knowledge – which he did both on account of the inadequacy and fallibility of the senses and on the grounds of there being no stable reality that could be known; and for undermining traditional morality by teaching that it is impossible to distinguish between right and wrong. The first two points of criticism find expression mainly in Plato's Protagoras and Theaetetus. The third emerges in Aristophanes' Clouds.

This perspective, very much influenced by Plato's general attitude to the Sophists, has been challenged recently, and the result is a reassessment of Protagoras' intellectual profile. Scholars have come to realize that the conceptual gap separating Socrates from the Sophists was not as great as Plato had posited. Socrates was, in fact, remarkably like them. Furthermore, in retrospect, Protagoras' positions often seem preferable to those of Plato. For instance, Protagoras' contention that the soul does not exist independently of the senses (Diog. Laert. 9.8.51) is borne out by modern neuroscience.

Today interest in Protagoras revolves around two doctrines and a mythical simile that survive in fragmentary form. The doctrine summarized in the proposition that "man is the measure of all things" (panton chrematon metron estin anthropos) is commonly (though not exclusively) taken to mean that sensory appearances and beliefs are objective truths, not subjective opinions. However, the mode of thinking underlying this claim had already been exposed as self-refuting in antiquity: if all beliefs are true, then the belief that all beliefs are not true is also true (Pl. Tht.).

Protagoras' agnosticism is summed up in a sentence that supposedly opened a work entitled On the Gods, quoted by Diogenes Laertius (9.8.51): "Concerning the gods I am unable to discover whether they exist or not, or what they are like in form; for there are many hindrances to knowledge, the obscurity of the subject and the brevity of human life." It has been noted that, unlike the other Presocratic atheists, Protagoras is not denying the existence of either supernatural powers or polytheistic gods. He is merely providing reasons for suspending judgment.

According to the mythical simile attributed to Protagoras by Plato, men, after being created and provided with a "divine portion," banded together to combat wild beasts. However, once they had done so and had founded cities, "they did wrong to one another through the lack of civic art (politike techne), and thus they began to be scattered again and to perish." The attempt to found cities finally succeeded thanks to divine intervention. Zeus, fearing man's destruction, "sent Hermes to bring shame (aidos) and right (dike) among men, to the end that there should be regulation of cities and friendly ties to draw them together" (Prt. 322b–c). The simile foreshadows the modern idea of social contract.

Eclipsed in antiquity by Plato and underrated in modern times, Protagoras deserves renewed attention.


Panhellenism; Philosophy, Classical Greece.

References and Suggested Readings
  • Diels, H.; Kranz, W. (1952) Die Fragmente der Vorsokratiker, 6th ed., vol. 2. Berlin.
  • Guthrie, W. K. C. (1969) A history of Greek philosophy, vol. 3. Cambridge.
  • Kassel, R.; Austin, C. (1983-) Poetae comici Graeci. Berlin.
  • Kerferd, G. B. (1981) The sophistic movement. Cambridge.
  • Wallace, R. W. (2007) Plato's sophists, intellectual history after 450, and Sokrates. In L. J. Samons II, ed., The Cambridge companion to the age of Pericles: 215-37. Cambridge.
  • Gabriel Herman
    Wiley ©2012

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