When a person, and especially a talented one, dies young, people sometimes mourn not just what they have in fact lost, but what might have been. But is mourning what might have been predicated on the belief that things could have been otherwise? And if someone is a thoroughgoing determinist and thinks that there's only one way things ever could have turned out, would it be irrational for such a person to mourn what might have been?

One way to interpret the mourner's state of mind is this: the mourner is thinking (optimistically) about the life the young person would have led had he/she not died young. That state of mind is consistent with believing that the young person's death was fully determined by the initial conditions of the universe in combination with the laws of nature.

The deterministic mourner might even recognize that, in mourning the young person's death, the mourner is committed to regretting that the Big Bang occurred just the way it did or that the laws of nature are just as they are: for only if the Big Bang or the laws of nature (or both) had been appropriately different would the young person not have died young. Furthermore, determinism allows that they could have been different. Determinism doesn't say that the initial conditions and the laws of nature are themselves causally determined; that would require causation to occur before any causation could occur.

Although the deterministic mourner's regret may sound odd, it doesn't strike me as irrational. The young person's early death is a painful but deterministic result of the laws of nature and the initial conditions of the universe -- and therefore one reason to regret that the laws and conditions were not appropriately different.