In An Essay Concerning Human Understanding, first published in 1690, John Locke (1632-1704) provides a complete account of how we acquire everyday, mathematical, natural scientific, religious and ethical knowledge. Rejecting the theory that some knowledge is innate in us, Locke argues that it derives from sense perceptions and experience, as analysed and developed by reason. While defending these central claims with vigorous common sense, Locke offers many incidental - and highly influential - reflections on space and time, meaning, free will and personal identity. The result is a powerful, pioneering work, which, together with Descartes's works, largely set the agenda for modern philosophy.