Socrates believed self-knowledge was essential. Today, we wonder if there’s even a self to know

The words ‘know thyself’ (or ‘gnothi seauton’ in Ancient Greek) were famously inscribed above the forecourt at the Temple of Apollo at Delphi. In Plato’s telling, Socrates believed that the value of self-knowledge consisted in one’s ability to recognise the limits of what they know, which, Socrates ultimately thought, was nothing. In the centuries since, thinkers who have tried to discern the nature of the self have come to radically different conclusions. Thomas Hobbes advocated introspection – attention to one’s own thoughts, feelings and desires – as a means to understanding others. Sigmund Freud developed his theory of the unconscious, introducing the notion that much of what makes up the self is hidden and unknowable. And in the contemporary era, the experimental psychologist Bruce Hood has turned to brain research to fundamentally question whether there is any self to know.