Several incidents in my life have convinced me of spiritual interposition - of the promptings of some beneficent force outside ourselves, which tries to help us where it can.

It is a capital mistake to theorize before you have all the evidence. It biases the judgment.

There are fifty who can reason synthetically for one who can reason analytically.

He had never seen a woman doctor before, and his whole conservative soul rose up in revolt at the idea. He could not recall any biblical injunction that the man should remain ever the doctor and the woman the nurse, and yet he felt as if a blasphemy had been committed.

The most difficult crime to track is the one which is purposeless.

Indeed, I cannot think why the whole bed of the ocean is not one solid mass of oysters, so prolific the creatures seem. Ah, I am wandering! Strange how the brain controls the brain! What was I saying, Watson?

Ex-Professor Moriarty of mathematical celebrity... is the Napoleon of crime, Watson.