The mind, like the body, has its contagious diseases and its scurvy. ...We catch everything from those with whom we come in contact; their gestures, their accent, etc.

The soul follows the progress of the body, as it does the progress of education.

One needs only eyes to see the necessary influence of old age on reason.

The human body is a machine which winds its own springs.

Let us... take in our hands the staff of experience... To be blind and to think that one can do without this staff is the worst kind of blindness.

Either everything is illusion, nature as well as revelation, or experience alone can explain faith.

Man... whatever the origin of his soul, if it is pure, noble, and lofty, it is a beautiful soul which dignifies the man endowed with it.

If there is a revelation, it can not then contradict nature.

I reduce to two the systems of philosophy which deal with man's soul. The first and older system is materialism; the second is spiritualism.

It is not enough for a wise man to study nature and truth; he should dare state truth for the benefit of the few who are willing and able to think.