In this talk I’ll present some of the main themes in my book of the same title. First, there are two general kinds of moral problems: The original moral problem is the problem of cooperation, the “Tragedy of the Commons”—Me vs. Us. Distinctively modern moral problems are different. They involve what I call the “Tragedy of Commonsense Morality,” which is about conflicting values and interests across social groups—Us vs. Them. Second, there two general kinds of moral thinking: “fast” intuitive thinking that is efficient but inflexible, and “slow” moral reasoning that is flexible but inefficient. I’ll present evidence that “fast” thinking is good for solving more basic moral problems (Me vs. Us), but that we need “slow” moral thinking to handle modern moral problems (Us vs. Them).