What is economics fundamentally about? Some say 'money'. But that only applies, at a stretch, to macroeconomics. Others say 'incentivised choices'. Through a review of the history and methodology of economics, with special concentration on the past 60 years, the book shows why the second answer is more accurate. But this leads straight into another problem: psychologists study choices too. So how is economics different from psychology? The book explains this, by showing how economics is really about groups or populations of people. In clearly distinguishing economics from psychology, the book criticizes the current popular wave of behavioural economics, showing how many studies under that label confuse economics with psychology. But if economics is about structures of group response, then how is it different from sociology? The book shows how and why economics and sociology are currently converging, perhaps ultimately to form a single unified discipline fed by two distinct historical tributaries.