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

There is nothing more deceptive than an obvious fact.

'Men die of the diseases which they have studied most,' remarked the surgeon, snipping off the end of a cigar with all his professional neatness and finish. 'It's as if the morbid condition was an evil creature which, when it found itself closely hunted, flew at the throat of its pursuer. If you worry the microbes too much they may worry you. I've seen cases of it, and not necessarily in microbic diseases either. There was, of course, the well-known instance of Liston and the aneurism; and a dozen others that I could mention.'

What can we know? What are we all? Poor silly half-brained things peering out at the infinite, with the aspirations of angels and the instinct of beasts.

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.

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

When we think how narrow and devious this path of nature is, how dimly we can trace it, for all our lamps of science, and how from the darkness which girds it round great and terrible possibilities loom ever shadowly upwards, it is a bold and a confident man who will put a limit to the strange by-oaths into which the human spirit may wander.