13. Self-Interest Part 2
Another way to look at the question of self-interest is from a biological point of view. In this perspective, self-interest could be defined as those actions which make one's genes more likely to be passed on, with selflessness defined as those actions which make ones genes less likely to be passed on. The concept of natural selection would, at first glance, seem to indicate that any organism that exhibited selfless behaviour would find itself reproducing at a lower rate than the competition and would eventually be made extinct.
This analysis is complicated, of course, by the fact that we share genes with various family members. So, if we followed a strictly selfish-gene style of behaviour, we would place full weight on our own interests, half weight on the interests of our siblings and parents and children, or a 1/8 weight on first cousins and so on, with our willingness to value the interests of others declining as their closeness to us and likelihood of sharing genes with us declines as well.
Biologists generally refer to this idea as the theory of kin selection.
That's about all I have to say on the topic of self-interst for now, other than to
note how well the idea of kin selection - where our ethical identification with people is strongest with those closest and weakens the more distant people are - lines up with Hume's notion of an ethical sense that functioned in the same manner as visual perspective, with objects further away registering as smaller on our ethical consciousness.