‎A change of work is the best rest.

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

There is nothing more stimulating than a case where everything goes against you.

Violence does, in truth, recoil upon the violent, and the schemer falls into the pit which he digs for another.

He [Professor Moriarty] is the Napoleon of crime, Watson. He is the organizer of half that is evil and of nearly all that is undetected in this great city. He is a genius, a philosopher, an abstract thinker. He has a brain of the first order.

What you do in this world is a matter of no consequence. The question is, what can you make people believe that you have done?

You're not hurt, Watson? For God's sake, say that you are not hurt!" It was worth a wound -- it was worth many wounds -- to know the depth of loyalty and love which lay behind that cold mask. The clear, hard eyes were dimmed for a moment, and the firm lips were shaking. For the one and only time I caught a glimpse of a great heart as well as of a great brain. All my years of humble but single-minded service culminated in that moment of revelation.