Literature ... seeks to entertain — and why is this? ... The reason, fundamentally, is that literature knows something that science does not: the hum… - Harvey Mansfield

The way out from complication and doubt is to reduce the good to pleasure, something close to the body, or to utility, something useful to the body. ... The body is considered as a factor all human beings have in common, hence an easy basis for generalization.

The social sciences are in a special difficulty because they cover the same field of human behavior as literature. As science, they must claim to improve upon the prejudice and superstition of common sense, and are therefore compelled to restate the language of common sense, full of implication and innuendo, in irreproachable, blameless, scientific prose innocent of bias or any other subtlety.

Self-interest, when simple, is universal; I would do the same as you. I would be propelled toward an obvious good, or toward a good I thought obvious. If self-interest is obvious, it is not really your very own; it has been generalized, perhaps artificially.