  First, one could challenge rational egoism, not only with the instrumental theory, but also with the “present-aim” theory of rationality. According to the present-aim theory, I have most reason to do what maximizes the satisfaction of my present desires. Even if all of these desires are self-regarding, the present-aim theory need not coincide with rational egoism. Suppose I know that in the future I will desire a good pension, but I do not now desire a good pension for myself in the future; I have different self-regarding desires. Suppose also that, looking back from the end of my life, I will have maximized my welfare by contributing now to the pension. Rational egoism requires that I contribute now. The present-aim theory does not. It claims that my reasons are relative not only to who has a desire — me rather than someone else — but also to when the desire is held — now rather than in the past or future.  The obvious justification an egoist could offer for not caring about time — that one should care only about the amount of good produced — is suicidal, since that should lead one not to care about who receives the good.  One reason the present-aim theory is important is that it shows there is a coherent, more minimal alternative to rational egoism. The rational egoist cannot argue that egoism is the most minimal theory, and that standard moral theories, by requiring more of people, require special, additional justification.  (For a very different argument to show again that an alternative to morality is less minimal than expected — directed more at the instrumental theory than rational egoism — see Korsgaard 2005.)