From somewhere, back in my youth, heard Prof say, 'Manuel, when faced with a problem you do not understand, do any part of it you do understand, then look at it again.' He had been teaching me something he himself did not understand very well—something in math—but had taught me something far more important, a basic principle.

If an elderly respected expert in a given field tells you that something can be done he is almost certainly right. If an elderly respected expert in a given field tells you that something is impossible, he is almost certainly wrong.

Remember this: once the human race is established on more than one planet and especially, in more than one solar system, there is no way now imaginable to kill off the human race.

Men are more sentimental than women. It blurs their thinking.

Money is a powerful aphrodisiac but flowers work almost as well.

Duty is a debt you owe to yourself to fulfill obligations you have assumed voluntarily.

Unarmed hand-to-hand fighting does not change through the ages; only the name changes, and it has only one rule: do it first, do it fast, do it dirtiest.