One of the most serious ethical reasons offered for preventing a suicide is that the suicide will one day be grateful - that is, that a person's values change over time. The suicide might wish to die now - might value death, or an end to suffering or experience, above all else - but perhaps once rescued and medicated, or perhaps years from now, the person will value life again, and will be happy to have been saved. Today's suicide could be tomorrow's reformed suicide.
Some have modeled human existence as consisting of a set of successive selves, such that we might describe the different values, characteristics, and interests of a person at time t, compared to those of that "same" person at time t-sub-one. Is it permissible, then, for an outsider to forcibly intervene in a person's action at time t, in the interests of protecting the interests of that person at time t-sub-one?
Certainly, I have heard reports of people attempting suicide, being "rescued," and eventually being grateful and glad to be alive after the fact. It is often assumed that the status of being grateful in the future is a good reason to intervene with force. But the accident of whether someone at time t-sub-one is, in fact, grateful for the intervention at time t seems like a poor justification for intervening at time t. First, there is a problem with whether the outsider actually has better information than the person at time t. Second, as I alluded to in my earlier post on depressed cognition and value, there is a question as to whether this "better information" might not, in fact, be a different set of values held by the outsider and mentally imposed on the hypothetical person at t-sub-one. Third, even if the outsider really possesses better information than the actor at time t, "better information" is not a complete justification for forcibly intervening in the actions of another. (I know alcohol is bad for you; please hand over that pitcher of Pliny the Elder, thank you very much, it's for your own good. Give me those garlic fries, too. Very high in fat.) And why would it be appropriate to force the person at time t to suffer unbearably for the benefit of the person at time t-sub-one?
My proposition has two parts: first, those who would forcibly intervene to prevent a suicide are unlikely to have better information than the suicide about his future values; second, even if outsiders have better information than the suicide and can somehow prove that the suicide will be happy in a few years' time, that still does not justify forcing the person to remain alive.