"The most difficult crime to track is the one which is purposeless."

"My mind rebels at stagnation. Give me problems, give me work, give me the most abstruse cryptogram or the most intricate analysis, and I am in my own proper atmosphere. I can then dispense with artifi…"

"It may be that you are not yourself luminous, but that you are a conductor of light. Some people without possessing genius have a remarkable power of stimulating it."

"The Germans are a brutal race, and must be crushed."

"It is my belief, Watson, founded upon my experience, that the lowest and vilest alleys in London do not present a more dreadful record of sin than does the smiling and beautiful countryside."