 So far we have been considering decisions in which one’s payoff comes in a single ‘hit’: a reward (or punishment) comes all at once. However, we can also consider cases in which one is to choose between different infinite utility streams—e.g., streams of finite daily utility that accumulate over an infinite future. There is an obvious candidate for evaluating the utility of a finite stream: add the utilities along the stream. But this method is not available when we have an infinite stream; we require additional principles to help us evaluate such streams, and it is not obvious what those principles should be.