The problem of meaning is created by limits, by being just this, by being merely this. The young feel this less strongly. Although they would agree, if they thought about it, that they will realize only some of the (feasible) possibilities before them, none of these various possibilities is yet excluded in their minds. The young live in each of the futures open to them. The poignancy of growing older does not lie in one’s particular path being less satisfying or good than it promised earlier to be — the path may turn out to be all one thought. It lies in traveling only one (or two, or three) of those paths. Economists speak of the opportunity cost of something as the value of the best alternative foregone for it. For adults, strangely, the opportunity cost of our lives appears to us to be the value of all the foregone alternatives summed together, not merely the best other one. When all the possibilities were yet still before us, it felt as if we would do them all.

— Robert Nozick, Philosophical Explanations

We live out our lives, both individually and in our relationships with each other, in the light of certain conceptions of a possible shared future, a future in which certain possibilities beckon us forward and others repel us, some seem already foreclosed and others perhaps inevitable. There is no present which is not informed by some image of some future and an image of the future which always presents itself in the form of a telos — or of a variety of ends or goals — towards which we are either moving or failing to move in the present. Unpredictability and teleology therefore coexist as part of our lives; like characters in a fictional narrative we do not know what will happen next, but nonetheless our lives have a certain form which projects itself towards our future. Thus the narratives which we live out have both an unpredictable and a partially teleological character. If the narrative of our individual and social lives is to continue intelligibly — and either type of narrative may lapse into unintelligibility — it is always both the case that there are constraints on how the story may continue and that within those constraints there are indefinitely many ways that it can continue.

— Alasdair MacIntyre, After Virtue, 2nd. ed.