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.

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

Far away on the path we saw Sir Henry looking back, his face white in the moonlight, his hands raised in horror, glaring helplessly at the frightful thing which was hunting him down. But that cry of pain from the hound had blown all our fears to the winds. If he was vulnerable he was mortal, and if we could wound him we could kill him. Never have I seen a man run as Holmes ran that night.

And yet the motives of women are so inscrutable. You remember the woman at Margate whom I suspected for the same reason. No powder on her nose - that proved to be the correct solution. How can you build on such a quicksand? Their most trivial action may mean volumes, or their most extraordinary conduct may depend upon a hairpin or a curling tongs.

Dogs don't make mistakes.

The more we progress the more we tend to progress. We advance not in arithmetical but in geometrical progression. We draw compound interest on the whole capital of knowledge and virtue which has been accumulated since the dawning of time.

I consider that a man's brain originally is like a little empty attic, and you have to stock it with such furniture as you choose. [...] It is a mistake to think that that little room has elastic walls and can distend to any extent. [...] It is of the highest importance, therefore, not to have useless facts elbowing out the useful ones.