Robert A. Heinlein

A zygote is a gamete's way of producing more gametes. This may be the purpose of the universe.

The best thing about the future was that it was unknown. Cassandra’s one good quality was that she was never believed.

The most preposterous notion that H. sapiens has ever dreamed up is that the Lord God of Creation, Shaper and Ruler of all the Universes, wants the saccharine adoration of His creatures, can be swayed by their prayers, and becomes petulant if He does not receive this flattery. Yet this absurd fantasy, without a shred of evidence to bolster it, pays all the expenses of the oldest, largest, and least productive industry in all history.

Waking a person unnecessarily should not be considered a capital crime. For a first offense, that is.

If heredity were not overwhelmingly more important than environment, you could teach calculus to a horse.

I see no use in written marriage contracts; they can’t be enforced...whereas if the partners want to make it work, no written instrument is necessary.

The historicity of Jesus is the slipperiest question in all history because for centuries the question couldn’t be raised. They would hang you for asking — or burn you at the stake.

The correct way to punctuate a sentence that starts: “Of course it is none of my business but — ” is to place a period after the word “but.” Don’t use excessive force in supplying such a moron with a period. Cutting his throat is only a momentary pleasure and is bound to get you talked about.

I'll find a tutor — no, Laz, not a horizontal one. Don’t you ever think about anything else?

(Come to think of it, dear, what else is worth thinking about? Money?)

Climate is what you expect, weather is what you get.

The second most preposterous notion is that copulation is inherently sinful.

Freedom begins when you tell Mrs. Grundy to go fly a kite.