A classical aphorism (Greek: gnothi seauton), reportedly incised in the wall of the Temple of Apollo at Delphi in Greece (along with other aphorisms, including "Nothing in excess").
The saying is attributed to a number of different sources - ranging from Apollo himself to Thales, or another of the Seven Sages. A precise attribution is unattainable, however.
According to Aristotle, this aphorism was supposedly the inspiration for Socrates' philosophical method.
The saying is also sometimes encountered in its Latin form, nosce te (ipsum) which goes back to Cicero.