Altruism, Self-Interest, and Reason
There are some in Christianity who throw into question the idea that altruistic action is good out of the consideration that such action can be pleasurable, rewarding or fulfilling to the self.
My response is that such action should be pleasurable, rewarding, and fulfilling to the self by matter of nature and reason. Someone who has evolved as himself, as part of humanity, and as part of life, will have natural inclinations to benefit all of the preceding. The pleasure or ego reward being gained from altruistic activity is thus congruent with nature and rationality. Such activity should be rewarding; and I for one found it more personally fulfilling to do volunteer work for charities than I did to work in a number of professional settings.
But under that argument that is floated by some Christians is the real problem. And that is: Conception held by some in Christianity that, if something is pleasant or rewarding, then it cannot be good. I can find no more sadistic evil in the world than this line of thinking. For beings that exist as part of life, and that have evolved over billions of years for the benefit of life - and millions of years for the benefit of their species - to take action that benefit their species and nature would be natural. And if such things are pleasurable or rewarding, then they are pleasurable and rewarding by nature of mechanisms that brought us about. These actions improve the survival and benefit of human species; they also enhance the well-being of life. And if they are satisfying or rewarding, that is only a function of nature and rationality.
In nature, we find altruism as much as we find self-interest; indeed we find in nature all sorts of behaviors that we also see in people. And one interesting new discovery is that there is an altruism gene that is present in some people more than it is in others. By that, it becomes understandable why some people tend to altruistic activity and others do not. Some are more naturally wired that way; others aren't. And that too should not be surprising.
My solution to all of this is, Live and let live. Let altruists be altruists; let the self-interested be self-interested; and recognize the contributions that come from both. In most people, we will find tendencies both toward altruism and toward self-interest; meaning that it would be natural for them to take both directions. And that too is rational, natural and good.