Who knows what I want to do? Who knows what anyone wants to do? How can you be sure about something like that? Isn't it all a question of brain chemistry, signals going back and forth, electrical energy in the cortex? How do you know whether something is really what you want to do or just some kind of nerve impulse in the brain. Some minor little activity takes place somewhere in this unimportant place in one of the brain hemispheres and suddenly I want to go to Montana or I don't want to go to Montana. (White Noise, Don DeLillo)

There has been a recent upsurge of research on moral judgment and decision making. One important issue with this body of work concerns the relative advantages of calculating costs and benefits versus adherence to moral rules. The general tenor of recent research suggests that adherence to moral rules is associated with systematic biases and that systematic cost-benefit analysis is a normatively superior decision strategy. This article queries both the merits of cost-benefit analyses and the shortcomings of moral rules. We argue that outside the very narrow domain in which consequences can be unambiguously anticipated, it is not at all clear that calculation processes optimize outcomes. In addition, there are good reasons to believe that following moral rules can lead to superior consequences in certain contexts. More generally, different modes of decision making can be seen as adaptations to particular environments.