Dying for a reason - suicide
I am inclined to say that rational action just is action done for a reason or (I'll concede at a stretch) for an 'all things considered' reason or set of reasons. Not in the least inclined to suicide myself, I can easily imagine that someone might consider they have a reason, even an all things considered reason, to end their own lives. If they act on this, they act rationally. Only if you build in an assumption that it is necessarily irrational to (want to) end one's life, is their action irrational.
But where does that assumption come from ? What reason do we have to accept it ? Without it, there is no case for saying that killing oneself for a reason is ever irrational, let alone always so. If there is a divine command not to commit suicide, then either that command is evident to reason, in which case one does not have an 'all things considered' set of reasons for committing suicide since this reason is not considered, or it is not evident to reason, in which case it has no place in one's reasons for action. If one accepts the divine command on grounds of faith, not reason, then one has a reason to act on one's faith and eschew suicide. But in this case again, one does not have an 'all things considered' set of reasons for committing suicide since this different reason
- of faith - is not considered. Whether faith itself is rational is another issue : still I would say that even if faith is irrational, if one believes in it one is rational in acting on it.
But all this only shows at most they are can be conditions on which it would not be rational to commit suicide, not that it is always irrational simpliciter to do so.
Dying for a reason - dying for a cause
Rosa Luxemburg : 'Being human means joyfully throwing your whole life "on the scales of destiny" when need be but all the while rejoicing in each sunny day and every beautiful cloud' (Quoted in Raya Dunayevskaya, Luxemburg, Women's Liberation and Marx's Philosophy of Revolution', init.)
I rather think that the rationality of suicide is not your principal concern. You are thinking, I take it, of dying for a cause - a religion, a personal or political faith, or a moral imperative to save another person. This kind of thing. But the same arguments advanced for the rationality of suicide carry straight across. If the promotion of a religion, a personal or political faith, or the moral imperative of a situation, gives you a reason or an 'all things considered' reason or set of reasons to relinquish your own life then no irrationality is involved in sacrificing yourself. How should it be ?
Ah but, comes the reply. You have forgotten a vital connexion :
Rationality and self-interest
If we make a privileged connexion between rationality and self-interest, the cases above are put in doubt. Or some of them. It hardly serves my self-interest to lose my life in a blaze in order to save a child. But there is no such privileged connexion. The connexion is between rationality and one's 'interests' (not self-interest unless this happens to be among one's interests), that is, the things and matters and people that concern one. They and the risks and opportunities to which they are open can certainly provide reasons for action, even for action at the cost of one's life.
Doesn't the quotation from Rosa Luxemburg express your entire position ?