Trust - our belief in the truth or reliability of someone or something - lies at the very heart of our relationships, our society and our everyday lives. Much of the time we take it for granted. And yet trust, or the lack of it, is becoming an increasingly prominent issue in public life: politicians say they want to rebuild trust in politics; people look for new ways to trust each other in a world where relationships are easier to start and harder than ever to sustain; and we are no longer sure how much we trust experts on issues like the safety of food or medicine. This short but thought-provoking book reveals why scientists, social scientists, and philosophers no longer take trust for granted. Beginning with some fascinating biological puzzles about the origins of trust -- how cooperation can evolve from 'selfish genes', and how language could have evolved when 'words are cheap' and we have such a capacity to deceive each other - Marek Kohn explores many different perspectives from the fields of science, sociology, economics, and politics, to draw out the wider implications for trust in human society today. The book ends on a personal note, concluding that our material prosperity is not matched by the quality of our lives and relationships, but that, if we understand what makes trust possible, and why it matters, then we will live better lives in a fast-moving, fast-changing, globalized society.