Cratylus was an ancient Athenian

History of Athens

Athens is one of the oldest named cities in the world, having been continuously inhabited for at least 7000 years. Situated in southern Europe, Athens became the leading city of Ancient Greece in the first millennium BCE and its cultural achievements during the 5th century BCE laid the foundations...

 philosopher from late 5th century BC, mostly known through his portrayal in Plato

Plato

Plato , was a Classical Greek philosopher, mathematician, student of Socrates, writer of philosophical dialogues, and founder of the Academy in Athens, the first institution of higher learning in the Western world. Along with his mentor, Socrates, and his student, Aristotle, Plato helped to lay the...

's dialogue Cratylus

Cratylus (dialogue)

Cratylus is the name of a dialogue by Plato. Most modern scholars agree that it was written mostly during Plato's so-called middle period...

. Little is known of Cratylus or his mentor Heraclitus

Heraclitus

Heraclitus of Ephesus was a pre-Socratic Greek philosopher, a native of the Greek city Ephesus, Ionia, on the coast of Asia Minor. He was of distinguished parentage. Little is known about his early life and education, but he regarded himself as self-taught and a pioneer of wisdom...

 (of Ephesus

Ephesus

Ephesus was an ancient Greek city, and later a major Roman city, on the west coast of Asia Minor, near present-day Selçuk, Izmir Province, Turkey. It was one of the twelve cities of the Ionian League during the Classical Greek era...

, Asia Minor). According to Cratylus at 402a, Heraclitus proclaimed that one cannot step twice into the same stream. According to Aristotle

Aristotle

Aristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...

 (Metaphysics

Metaphysics (Aristotle)

Metaphysics is one of the principal works of Aristotle and the first major work of the branch of philosophy with the same name. The principal subject is "being qua being", or being understood as being. It examines what can be asserted about anything that exists just because of its existence and...

, 4.5 1010a10-15), his disciple Cratylus went a step further to proclaim that it cannot even be done once. Such was his thorough-going skepticism.

If the world was in such constant flux that streams could change instantaneously, then so could words. Thus, Cratylus found communication to be impossible without exactly defined words. Cratylus shows why advanced communication needs etymology and modern scientific definitions. As a result of this realization, Cratylus renounced 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

Cratylism

Cratylism is a philosophical theory based on the teachings of Cratylus also known as Kratylos. Vaguely exegetical, it holds that the fluid nature of ideas, words, and communications leaves them fundamentally baseless, and possibly unable to support logic and reason.-External links:*...

 is based on "reconstituted" teachings, owing mostly to Cratylus's and Heraclitus

Heraclitus

Heraclitus of Ephesus was a pre-Socratic Greek philosopher, a native of the Greek city Ephesus, Ionia, on the coast of Asia Minor. He was of distinguished parentage. Little is known about his early life and education, but he regarded himself as self-taught and a pioneer of wisdom...

's inclusion in the Dialogues of Plato.