We must doubt the certainty of everything which passes through the senses, but how much more ought we to doubt things contrary to the senses, such as the existence of God and the soul.

Learning is the only thing the mind never exhausts, never fears, and never regrets.

One day the world will look upon research upon animals as it now looks upon research on human beings.

I roamed the countryside searching for answers to things I did not understand.

The natural desire of good men is knowledge.

The art of procreation and the members employed therein are so repulsive, that if it were not for the beauty of the faces and the adornments of the actors and the pent-up impulse, nature would lose the human species.

The sun gives spirit and life to the plants and the earth nourishes them with moisture.