“Know thyself” (Greek: Γνῶθι σεαυτόν, gnōthi seauton)[a] is a philosophical maxim which was inscribed upon the Temple of Apollo in the ancient Greek precinct of Delphi.
The maxim was re-interpreted by Plato, who understood it to mean, broadly speaking, “know your soul”. One could acquire knowledge of the self by studying the universe, or knowledge of the universe by studying the self.
“When this man shall have surveyed the heavens, the earth, and the seas, and studied the nature of all things, and informed himself from whence they have been generated, to what state they will return, and of the time and manner of their dissolution, and has learnt to distinguish what parts of them are mortal and perishable, and what divine and eternal — when he shall have almost attained to a knowledge of that Being who superintends and governs these things, and shall look on himself as not confined within the walls of one city, or as the member of any particular community, but as a citizen of the whole universe, considered as a single Commonwealth: amid such a grand magnificence of things as this, and such a prospect and knowledge of nature, what a knowledge of himself, O ye immortal Gods, will a man arrive at! That is the warning of the Pythian Apollo.”