An exploration of some of the most important and enduring ideas in human history – from religion, science, philosophy, medicine, psychology, politics, economics and art – each presented in brief, accessible form. 'Big' ideas are those concepts and theories that have radically transformed our understanding of the world we live in, our place in that world and the ways we have shaped the past and will shape the future. They are the ideas that have had a huge impact on human civilization – and they come from all disciplines of human ingenuity. This concise, accessible and multi-faceted book provides an essential introduction to 150 of the most important principles of Western thought.