Central to this book is the further assumption that man is a rational utility maximizer in all areas of life, not just in his economic affairs, that is, not only when engaged in buying and selling in explicit markets. This idea goes back to jeremy Bentahm in the eighteenth and early nineteenth century, but received little attention from economists until the work of Gary Becker in th 1950s and 1960s.
The concept of man as a rational maximizer implies that people respond to incentives.(...) From this proposition derive the three fundamental principles of economics.

Ch. 1: The Nature of Economic Reasoning - Economic Analysis of Law (7th ed., 2007)