[R]eason is... given to us as a practical faculty, that is, as one that influences the will.

The question is not so much whether there is life on Mars as whether it will continue to be possible to live on Earth

Innocence is indeed a glorious thing; but, unfortunately, it does not keep very well and is easily led astray.

Morality is not properly the doctrine of how we may make ourselves happy, but how we may make ourselves worthy of happiness.

Two things awe me most, the starry sky above me and the moral law within me.

Procrastination is hardly more evil than grasping impatience.

The wise man can change his mind; the stubborn one, never.