A plausible account of what makes someone’s life better will be a “substantive good” account: a claim or set of claims about what things are good in themselves, not good because they are desired. Hedonism is one such an account; it is just an implausibly narrow one, a list that includes only one element.
Any account of what makes someone’s life go better, especially one that rests on claims about what is substantively good, is bound to be controversial. So one might ask (as some student in my course always does), “Who’s to decide what makes a life better?” It is important to see that this is a facile debating move, not a serious question. To say of some person that he is “the one to decide” whether A is the case or not suggests that this person has the authority to settle this question: that his deciding that A is the case would make it so. Sometimes, in some institutional settings, for example, there is authority of this kind. The Supreme Court, for example, has the authority to decide whether something is the law of the United States. But with respect to the questions we are considering there obviously is no authority of this kind. So the answer to the question “Who’s to decide?” is “No one.” That is to say, no one has the authority to settle the question.
But in another, more relevant, sense the answer to “Who’s to decide?” is “Each of us.” That is to say, it is up to each of us to make up his or her own mind about such questions as what makes a life better for the person who lives it. This is not to say that each of us has any authority to settle this question. It is up to each of us to assess the merits of competing answers and arrive at our own conclusion as to which one is correct. But whether this conclusion is correct depends on its merits, not on our decision.
It may seem that each person has special authority to settle the question of what life is the best life for him or her. This may be true in a sense, but not in the sense relevant to our present discussion. It is up to each person to decide how to live, and each person has authority over this question in the sense that (within limits, at least) his or her decision has a claim not to be interfered with. But authority of this kind should not be confused with authority to settle the question of what makes a life worth living—to determine, by one’s decision, what the right answer to this question is. We do not have this authority. We can be mistaken about what life would be best for us, although it is also true in many cases that our choices about how to live, even if misguided, ought not to be interfered with.
There is now a growing body of empirical investigations, by psychologists and economists, of what makes people happy, and it might be thought that these findings could provide an answer to the question we are considering. At the most fundamental level, this is not so. Philosophical questions, such as whether the quality of a life for the person who lives it depends only on the person’s experience, or only on what he or she desires, or also on something else, cannot be settled by taking a poll. The correctness of an answer depends on the merits of the argument supporting it, not on how many people believe it to be correct.