In the realm of ideas everything depends on enthusiasm... in the real world all rests on perseverance.

Someone criticized an elderly man for wooing young women. He replied that that was the only way to rejuvenation, which was, afterall, everybody's wish.

Nature is the living, visible garment of God.

Nature has neither core nor skin: she’s both at once outside and in.

A reasonable man needs only to practice moderation to find happiness.

The absence of temptation is the absence of virtue.

Should I not be proud, when for twenty years I have had to admit to myself that the great Newton and all the mathematicians and noble calculators along with him were involved in a decisive error with respect to the doctrine of color, and that I among millions was the only one who knew what was right in this great subject of nature?