It is a capital mistake to theorize before one has data.

I followed you.' I saw no one.' That is what you may expect to see when I follow you.

The more outre' and grotesque an incident is the more carefully it deserves to be examined, and the very point which appears to complicate a case is, when duly considered and scientifically handled, the one which is most likely to elucidate it.

I am a brain, Watson. The rest of me is a mere appendix.

Any truth is better than indefinite doubt.

You mentioned your name as if I should recognize it, but beyond the obvious facts that you are a bachelor, a solicitor, a freemason, and an asthmatic, I know nothing whatever about you.

I could not rest, Watson, I could not sit quiet in my chair, if I thought that such a man as Professor Moriarty were walking the streets of London unchallenged.