The Happiness Hypothesis: Finding Modern Truth in Ancient Wisdom is a 2006 psychology book by Jonathan Haidt written for a general audience. In it, Haidt poses several "Great Ideas" on happiness espoused by thinkers of the past – Plato, Buddha, Jesus and others – and examines them in the light of contemporary psychological research, extracting from them any lessons that still apply to our modern lives. Central to the book are the concepts of virtue, happiness, fulfillment, and meaning.