Anything seems commonplace, once explained.

There are always some lunatics about. It would be a dull world without them.

Healthy scepticism is the basis of all accurate observation.

He [Professor Moriarty] is the Napoleon of crime, Watson. He is the organizer of half that is evil and of nearly all that is undetected in this great city. He is a genius, a philosopher, an abstract thinker. He has a brain of the first order.

The future was with Fate. The present was our own.

It is fortunate for this community that I am not a criminal.

His ignorance was as remarkable as his knowledge. Of contemporary literature, philosophy and politics he appeared to know next to nothing... My surprise reached a climax, however, when I found incidentally that he was ignorant of the Copernican Theory and of the composition of the Solar System.