Outline of a Morality Without Obligation or Sanction https://www.marxists.org/archive/guyau/1885/morality.htm (1885).
Context: A third equivalent of duty is borrowed from sensibility and not, like the preceding, from intelligence and activity. It’s the growing fusion of sensibilities, and the ever increasing sociable character of elevated pleasures, from which results a kind of duty or superior necessity which pushes us naturally and rationally towards others. By virtue of evolution, our pleasures grow and become increasingly impersonal; we cannot experience enjoyment within our selves as if on a deserted isle. Our milieu, to which we better adapt ourselves every day, is human society, and we can no more be happy outside of this milieu than we can breathe outside the air. The purely selfish happiness of certain Epicureans is a chimera, an abstraction, an impossibility; the true human pleasures are all more or less social. Pure egoism, rather than being an affirmation of the self, is a mutilation of the self.
