@Ruthless Logic,
If we characterise
every conscious act as being caused by self-interest, does this tell us anything at all? Have we not so broadly defined "self-interest" as to be meaningless? And if every act is the result of "self-interest" then how do we account for the ordinary concept that some acts are NOT caused by it?
No matter how we examine the example provided, can we ignore that in throwing oneself on a grenade the soldier chooses his own destruction, and how would that choice be in his self-interest? For it would seem that self-preservation is the epitome of self-interest.
If, on the other hand, it is some
unconscious or automatic response to a situation, then there is no question of motive or choice, and thus "self-interest" does not even apply. Of course, someone may argue that any automatic, or "natural" action is one of self-interest, but then isn't it just a natural act, and self-interest becomes one (out of many) interpretations of Nature, and wouldn't the characterisation be a redundant description? It would certainly be, I would think, an unwarranted
ethical description of nature.