Hate always sells well, but for repeat trade and the long pull happiness is sounder merchandise.

The truth of a proposition has nothing to do with its credibility. And vice versa.

All cats are not gray after midnight.

But goodness alone is never enough. A hard, cold wisdom is required for goodness to accomplish good. Goodness without wisdom always accomplishes evil.

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.

Analogy is even slipperier than logic.

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