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.

So complex is the human spirit that it can itself scarce discern the deep springs which impel it to action.

What the deuce is it to me?" he interrupted impatiently: "you say that we go round the sun. If we went round the moon it would not make a pennyworth of difference to me or to my work.

...while the individual man is an insoluble puzzle, in the aggregate he becomes a mathematical certainty.

The stage lost a fine actor, even as science lost an acute reasoner, when [Holmes] became a specialist in crime.

Desultory readers are seldom remarkable for the exactness of their learning.

The emotional qualities are antagonistic to clear reasoning.