egoism

Egoism, broadly defined, is the philosophical view that one should maximize for their own utility function, or well-being, or self-satisfaction, etc…, whatever you want to call it. The general statement is that there is some value one would want to maximize for themselves. This philosophical view is a metaethical view in general but can be applied descriptively.

This view is a part of a broader view of consequentialism, a view that I broadly subscribe to; sometimes utilitarian analysis is useful for describing things inside the egoist framework, and sometimes it is not.

In economics, homo-econimus is a kind of idealized economic agent that maximizes for their own economic value. Descriptive egoism is in a sense the statement that people tend to maximize for some utility function. In a sense, there are many games that people can play, and economics is just one of them; there's homo-politicus, homo-vitamus, and many other games that agents try to play. Descriptive egoism is the descriptive formulation of a utility function that people have in-built, and a statement that people tend to play according to said utility functions with generalized rational expectations.

The perscriptive egoism is a meta-ethical framework that simply asserts that one should act in their own self interest. Self interest is a loosely defined term that is subjective to the individual.

Often many will point out the fact that it is a circular system, that it has no descriptive power because one can formulate anything in terms of an egoist outlook. Therefore, while one can accept or deny the validity of egoism, the framework of egoism has weak axioms and it is therefore possible to formulate many sub-philosophies that are compatible with egoism. (Meta-comment: I would describe myself as someone that formulates sub-philosophies inscribed within the egoist framework, and I would myself describe my own views in an egoist manner).