“The larger crimes are apt to be the simpler, for the bigger the crime, the more obvious, as a rule, is the motive.”

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

“The most common place crime is often the most mysterious, because it presents no new or specific features from which deductions may be drawn”

“As a rule, the more bizarre a thing is the less mysterious it proves to be. It is your commonplace, featureless crimes which are really puzzling, just as a commonplace face is the most difficult to identify.”

“There are no crimes and no criminals in these days. What is the use of having brains in our profession? I know well that I have it in me to make my name famous. No man lives or has ever lived who has brought the same amount of study and of natural talent to the detection of crime which I have done. And what is the result? There is no crime to detect, or, at most, some bungling villainy with a motive so transparent that even a Scotland Yard official can see through it.”

“Holmes took up the stone and held it against the light. "It's a bonny thing," said he. "Just see how it glints and sparkles. Of course it is a nucleus and focus of crime. Every good stone is. They are the devil's pet baits. In the larger and older jewels every facet may stand for a bloody deed. This stone is not yet twenty years old. It was found in the banks of the Amoy River in soutern China and is remarkable in having every characteristic of the carbuncle, save that it is blue in shade instead of ruby red. In spite of its youth, it has already a sinister history. There have been two murders, a vitriol-throwing, a suicide, and several robberies brought about for the sake of this forty-grain weight of crystallised charcoal. Who would think that so pretty a toy would be a purveyor to the gallows and the prison?”

“It's a wicked world, and when a clever man turns his brain to crime it is the worst of all.”