I had ... come to an entirely erroneous conclusion, which shows, my dear Watson, how dangerous it always is to reason from insufficient data.

Beyond the obvious facts that he has at some time done manual labour, that he takes snuff, that he is a Freemason, that he has been in China, and that he has done a considerable amount of writing lately, I can deduce nothing else.

A client is to me a mere unit, a factor in a problem.

If you had killed Watson, you would not have got out of this room alive.

They say that genius is an infinite capacity for taking pains," he remarked with a smile. "It's a very bad definition, but it does apply to detective work.

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

To a great mind, nothing is little,' remarked Holmes, sententiously.