To every action there is always opposed an equal reaction.

I can calculate the motion of heavenly bodies, but not the madness of people.

Physics, beware of metaphysics.

The degree and duration of the torment of these degenerate and anti-Christian people, should be no other than would be approved of by those angels who had ever labored for their salvation, and that Lamb who had redeemed them with his most precious blood.

What Descartes did was a good step. You have added much several ways, and especially in taking the colours of thin plates into philosophical consideration. If I have seen a little further it is by standing on the shoulders of Giants.

Gravity explains the motions of the planets, but it cannot explain who sets the planets in motion.

Every body persists in a state of rest or of uniform motion in a straight line, unless it is compelled to change that state by forces having impact upon it.