Expertise in one field does not carry over into other fields. But experts often think so. The narrower their field of knowledge the more likely they are to think so.

Love your country, but never trust its government.

I believe that this hairless embryo with the aching, oversize brain case and the opposable thumb, this animal barely up from the apes, will endure --will endure longer than his home planet, will spread out to the other planets, to the stars, and beyond, carrying with him his honesty, his insatiable curiosity, his unlimited courage --and his noble essential decency. This I believe with all my heart.

Marriage is a psychological condition, not a civil contract and a license. Once a marriage is dead, it is dead, and it begins to stink faster than a dead fish.

Throughout history, poverty is the normal condition of man. Advances which permit this norm to be exceeded — here and there, now and then — are the work of an extremely small minority, frequently despised, often condemned, and almost always opposed by all right-thinking people. Whenever this tiny minority is kept from creating, or (as sometimes happens) is driven out of a society, the people then slip back into abject poverty. This is known as "bad luck.

Working because you want to is the best sort of play.

Talking with a Martian is like talking with an echo. You don't get argument but you don't get results.