Egoism, n.
Etymology: [F. égoïsme, fr. L. -ego I. See I, and cf. Egotism.]
1. (Philos.)
The doctrine of certain extreme adherents or disciples of Descartes and Johann Gottlieb Fichte, which finds all the elements of knowledge in the ego and the relations which it implies or provides for.
2. Excessive love and thought of self; the habit of regarding one's self as the center of every interest; selfishness; -- opposed to altruism.
Shades of meaning
Fernald has no entry of its own for egoism; he lists it under egotism.
Where he writes about it:
Egoism is giving the "I" undue supremacy in thought; egotism is giving the "I" undue prominence in speech. — from egotism
Egotism is sometimes used in the sense of egoism, or supreme regard for oneself. — from egotism