The stage lost a fine actor, even as science lost an acute reasoner, when [Holmes] became a specialist in crime.

Crime is common. Logic is rare. Therefore it is upon the logic rather than upon the crime that you should dwell.

On glancing over my notes of the seventy odd cases in which I have during the last eight years studied the methods of my friend Sherlock Holmes, I find many tragic, some comic, a large number merely strange, but none commonplace; for, working as he did rather for the love of his art than for the acquirement of wealth, he refused to associate himself with any investigation which did not tend towards the unusual, and even the fantastic.

It is stupidity rather than courage to refuse to recognize danger when it is close upon you.

A man always finds it hard to realize that he may have finally lost a woman's love, however badly he may have treated her.

Well, I'm a bacteriologist, you know. I live in a nine-hundred-diameter microscope. I can hardly claim to take serious notice of anything that I can see with my naked eye.

To let the brain work without sufficient material is like racing an engine. It racks itself to pieces.