It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.

[Sherlock Holmes:] The temptation to form premature theories upon insufficient data is the bane of our profession.

Once or twice in my career I feel that I have done more real harm by my discovery of the criminal than ever he had done by his crime. I have learned caution now, and I had rather play tricks with the law of England than with my own conscience.

I cannot live without brainwork. What else is there to live for? Stand at the window here. Was ever such a dreary, dismal, unprofitable world? See how the yellow fog swirls down the street and drifts across the duncoloured houses. What could be more hopelessly prosaic and material?

Life, my dear Watson, is infinitely stranger than fiction; stranger than anything which the mind of man could invent. We could not conceive the things that are merely commonplace to existence. If we could hover over this great city, remove the roofs, and peep in at the things going on, it would make all fiction, with its conventionalities and foreseen conclusions flat, stale and unprofitable.

Is there any point to which you would wish to draw my attention?' To the curious incident of the dog in the night-time.' The dog did nothing in the night-time.' That was the curious incident,' remarked Sherlock Holmes.

It is a pity he did not write in pencil. As you have no doubt frequently observed, the impression usually goes through -- a fact which has dissolved many a happy marriage.