I keep the subject of my inquiry constantly before me, and wait till the first dawning opens gradually, by little and little, into a full and clear light.

To any action there is always an opposite and equal reaction; in other words, the actions of two bodies upon each other are always equal and always opposite in direction.

In the absence of any other proof, the thumb alone would convince me of God's existence.

Because of Diamond, I have had to begin much of the work afresh. I will not, however, rid myself of her, nor even punish her. She knew not what she was doing, and that which she did was for my protection and for love of my person. Her place remains at my side or against my feet when I lie abed.

All knowledge and understanding of the Universe was no more than playing with stones and shells on the seashore of the vast imponderable ocean of truth.

I have not been able to discover the cause of those properties of gravity from phenomena, and I frame no hypotheses; for whatever is not deduced from the phenomena is to be called a hypothesis, and hypotheses, whether metaphysical or physical, whether of occult qualities or mechanical, have no place in experimental philosophy.

A man may imagine things that are false, but he can only understand things that are true, for if the things be false, the apprehension of them is not understanding.