Cogito, ergo sum: many scholars believe Descartes ‘invented’ the idea of consciousness. Earlier thinkers such as Plato and Aristotle lacked the requisite word and therefore lacked the concept ––or so it is argued. This project challenges this outlook and reveals the richness of ancient theories of consciousness. Although the ancients did understand consciousness differently, the notion was fundamental to core areas of their philosophy: they saw it as definitive of life and key to self-realisation and fulfilment. Uncovering the role of consciousness in ancient philosophers’ thought, this research enables us to reappreciate their views and recognise their renewed relevance today.