Egoistical.

in an egoistic manner

Caring about oneself and the gratification of one's own desires rather than others. / (nonstandard, by confusion of the similar words) Egotistical (tending to talk excessively about oneself).

An advocate of egoism. / An egocentric or self-centered person. / (nonstandard, by confusion of the similar words) An egotist (person who talks excessively about themself).

plural of egoist

an advocate of rational egoism

plural of rational egoist