Having been raised Jewish, and having since found my own set of rational reasons to behave morally as an atheist, I've wondered about this for a long time.
Altruistic behavior, ISTM, is practically always rewarded in some fashion or another. If the altruist doesn't get a gift or recognition of some kind, she will at least be held in higher esteem by the recipient of the act and/or the witnesses of the act. This seems practically inevitable to me.
So, if altruism is defined as doing kind things for other people without the expectation of a reward, but altruists are always rewarded with at least some intangible sense of good will, and all altruists know this, is it actually possible to be altruistic?
That is, everybody who thinks about human behavior at all, expects some reward (as listed above) for altruistic behavior, so is it possible to actually commit kind acts without expecting any of those things to happen? I mean, you'd have to go beyond humility and into flat-out denial of human nature to not expect any of those kinds of rewards, right?