It is even possible that laws which have not their origin in the mind may be irrational, and we can never succeed in formulating them.

Shuffling is the only thing which Nature cannot undo.

Proof is an idol before whom the pure mathematician tortures himself.

Oh leave the Wise our measures to collate. One thing at least is certain, light has weight. One thing is certain and the rest debate. Light rays, when near the Sun, do not go straight.

It is sound judgment to hope that in the not too distant future we shall be competent to understand so simple a thing as a star.

It is one thing for the human mind to extract from the phenomena of nature the laws which it has itself put into them; it may be a far harder thing to extract laws over which it has no control.