Full Idea
If we observe an altruistic action the simplest explanation and the essential character of the person's conduct is that they make less distinction than is usually made between themselves and others.
Clarification
'Altruism' is self-sacrifice
Gist of Idea
Altruistic people make less distinction than usual between themselves and others
Source
Arthur Schopenhauer (The World as Will and Idea [1819], IV.66)
Book Reference
Schopenhauer,Arthur: 'The World as Will and Idea', ed/tr. Berman,Jill and David [Everyman 1995], p.234
A Reaction
Obvious, really, but Schopenhauer is talking about the will. Is the effacement of the Self desirable, apart from the benefit it might bring to other people. I don't find it appealing.