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This article is about the Athenian philosopher. For Plato's dialogue, see Cratylus (dialogue).

Cratylus (/krəˈtləs/; Ancient Greek: Κρατύλος, Kratylos) was an ancient Athenian philosopher from the mid-late 5th century BCE, known mostly through his portrayal in Plato's dialogue Cratylus. He was a radical proponent of Heraclitean philosophy and influenced the young Plato.


Little is known of Cratylus beyond his status as a disciple of Heraclitus of Ephesus, Asia Minor. The modern biographical tradition has not reached consensus on his approximate date of birth, arguing alternately for an age comparable roughly either to Plato or Socrates.[1] Cratylus is mentioned in Aristotle's Metaphysics in a passage which seems to imply that Cratylus was an established and active philosopher in Athens during the mid-late 5th century,[1] and that Plato himself became briefly interested in his work prior to aligning with Socrates.


In Cratylus' eponymous Platonic dialogue, the character of Socrates states Heraclitus' proclamation that one cannot step twice into the same stream.[2] According to Aristotle, Cratylus went a step beyond his master's doctrine and proclaimed that it cannot even be done once.[3]

If the world was in such constant flux that streams could change instantaneously, then so could words. Thus, at least according to the dialogue, Cratylus found communication to be impossible without exactly defined words. In the text, he argues that advanced communication needs etymology and modern scientific definitions. As a result of this realization, Cratylus renounces his power of speech and limited his communication to moving his finger, as a mere figurative gesture and not as an ideology. He was an advocate of the idea that language is natural rather than conventional.

The little known philosophy of Cratylism is based on "reconstituted" teachings, owing mostly to Plato's portrayal of Cratylus. His most pointed saying is a revision of an aphorism by Heraclitus: "One cannot step in the same river once." which takes flux to its necessary conclusion whereby the observer changes the world by any contact with it.

See also[edit]


  1. ^ a b Debra Nails. The People of Plato: A prosopography of Plato and other Socratics. Indianapolis: Hackett Publishing, 2002, pp. 105
  2. ^ Plato, Cratylus, 402a
  3. ^ Aristotle, Metaphysics, 4.5 1010a10-15