One of the great Chicago Ideas is the equivalence of positive and negative incentives. The government can motivate you by rewarding some behavior or by penalizing your failure to behave in the preferred manner. Private parties rarely have the authority to hit you with sticks, so they must usually begin with carrots, or positive inducements, unless law offers torts or other negative inducements in the background. But things quickly get more complicated. Rewards might draw people to an activity, and penalties might cause them to stay away, so that the carrots and sticks are not equivalent. How does law reflect these secondary effects? When is it a good idea to mix positive and negative rewards? Should we pay people not to commit crimes? Why didn’t any lawmakers try to pay people not to enter into same-sex marriages? Why not just impose higher taxes on people who do not engage in public service? This first lecture of the year in our Chicago’s Best Ideas series introduces some of these ideas and then takes them in surprising directions. Saul Levmore is the William B. Graham Distinguished Service Professor of Law.