You see, if the height of the mercury [barometer] column is less on the top of a mountain than at the foot of it (as I have many reasons for believing, although everyone who has so far written about it is of the contrary opinion), it follows that the weight of the air must be the sole cause of the phenomenon, and not that abhorrence of a vacuum, since it is obvious that at the foot of the mountain there is more air to have weight than at the summit, and we cannot possibly say that the air at the foot of the mountain has a greater aversion to empty space than at the top.

There are two equally dangerous extremes-to shut reason out, and to let nothing else in.

Men never do evil so completely and cheerfully as when they do it from religious conviction.

If I believe in God and life after death and you do not, and if there is no God, we both lose when we die. However, if there is a God, you still lose and I gain everything.

Man is neither angel nor beast.

Thought makes the whole dignity of man; therefore endeavor to think well, that is the only morality.

The multitude which does not reduce itself to unity is confusion.