Doing One's Best

To characterize behavior, we sometimes say, “He did the best he could.” If we unpack this sentence, it contains two elements: desires and opportunities. Desires define what, for the agent, counts as “the best.” Opportunities are the options or means that the agent “can” choose from. This characterization may also serve as a rudimentary rational-choice explanation of the behavior. If we ask, “Why did he do it?” the answer “It was the best he could do” may be fully sufficient. In many cases, more is needed to provide a satisfactory rational-choice explanation. In particular, we may need to appeal to the beliefs of the agents and not merely to desires and opportunities. These complications will concern us in Chapter 11. Here, I discuss how far the simple desire-opportunity framework can get us. I shall also suggest that the framework is sometimes not as simple as it might appear, since desires and opportunities are not always (as is sometimes assumed) independent of each other.

There is another, equivalent way of looking at the matter. In understanding behavior, we may begin with all the abstractly possible actions the individual might undertake. The action that we actually observe can be seen as the result of two successive filtering operations. The first filter is made up of all the constraints – physical, economic, legal, and others – that the agent faces. The actions consistent with all the constraints constitute the opportunity set.