Long ago Mr. Clemens demonstrated in his essay “What is man?” that every one of us acts at all times in his own interest. Once you understand this, it offers a way to negotiate with an antagonist in order to find means to cooperate with him for mutual benefit. But if you are convinced of your own “altruism” and you try to shame him out of his horrid selfishness, you will get nowhere.

— Robert A. Heinlein To Sail Beyond the Sunset (1987)

More quotes by Robert A. Heinlein

Stranger in a Strange Land (1961)

The Cat Who Walks Through Walls (1985)

I Will Fear No Evil (1970)

Time Enough for Love (1973)

The Door Into Summer (1957)

Quote text and notes from Wikiquote: Robert A. Heinlein (page history), available under CC BY-SA 4.0. Source quality and labels are our own summary of what Wikiquote records.