Egalitarianism is the belief or system itself — the -ism. It is the idea that people should be treated as equals and enjoy equal rights. Writers sometimes split it into kinds: political (equal civic rights), economic (a smaller gap in wealth), gender (women and men with the same standing). Formal. Same core as egalitarian, but you are naming the school of thought, not describing one law or one person. People praise a country’s egalitarianism, though actually wealth and voice may still sit with a few families; the word can name an ideal people argue over, not a clean photograph of life.