But how does this fit in with actions of self-sacrifice which are actions which are contrary to self-interest? Sometimes we rise above self-interest. What about that?
I don't think self-sacrifice ever rises above self-interest, but to make sense of this we have to recognize there are several aspects of consciousness we call "self."
From having a physical body (some would say, from being
a physical body) comes self traits of physical survival and physical desires. When we are acting to preserve or satisfy our physical existence and desires, and no other factors are in play, then we will fight hard to survive or get what we lust for. There are also traits we identify as "self" which come from conditioning, personal tastes, and personal aversions. All of the above, interestingly, was described by the Buddha as the acquired self
(FYI, I am not a Buddhist).
Some people claim, and seem able to demonstrate, that there is more self-potential than physical or acquired interests. For example, some of us give to others in various ways from love to charity. Why? Because it feels good to do so. Yes, there are people who give because, say, their religion tells them they should, and so get only whatever satisfaction one gets from living according to one's beliefs. But in either case, the reason a person gives is in hope of personal reward.
But let's add a bit of complication to the issue, such as your child is about to be burned alive and to save her you have to risk death (i.e., your self-sacrifice scenario). What feels worse to your self, to watch your child burn alive or to risk death? Socrates will be sentenced to death unless he conforms to Greek laws, but it is more painful for him to renounce his principles than it is to die. Jesus is faced with an agonizing death on the cross as an assignment from God (or so he believes), but his devotion to serving God is so great that it pains him more to not do God's bidding than it does to suffer on the cross.
So with both aspects of self, all actions are taken out of self-interest, it's just that what kind of person we are is determined by which self aspect is dominant in us. When the temporary, immediate, physical, wanting, needy self is king, then the deeper, more enduring, giving, caring self is stifled. We call that "selfish." Those of us who've come to love the deeper self know the "satisfaction" of the selfish self is very, very short-lived, requires constant resupplying, and never achieves the peace of lasting fulfillment.
I think to fully understand how, and especially why
, everything we do is out of self-interest, we also have to have clear insight into our own nature. We are feeling beings, everything we do attempts to work toward feeling good (and failing that, to avoid feeling bad). The reason there are miserable people is because much stuff we pursue we in hopes of feeling good actually makes us feel bad. Some people hate because they fear their hate object will make them feel bad. People take drugs to either feel good or escape feeling bad; even suicide is an effort to escape bad feeling. Eat, have sex, have a family, get rich, win the marathon, look beautiful . . . you name it, with it all we have our hopes pinned on it to makes us feel good.
If the need to feel good is our nature, then the real question is, what actually works in that regard? The selfish perspective is ME NOW, and often, NOT YOU if others might interfere with "me now." That person is looking to feel good, and so is self-interested. But so is the saint who is giving of himself, it's just that he is looking to feel good by relying on a whole other aspect of his being . . . an aspect that I have observed seems to make one feel more deeply and lastingly good.