“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.”

“It is a mistake to confound strangeness with mystery. The most commonplace crime is often the most mysterious because it presents no new or special features from which deductions may be drawn. This murder would have been infinitely more difficult to unravel had the body of the victim been simply found lying in the roadway without any of those outré and sensational accompaniments which have rendered it remarkable. These strange details, far from making the case more difficult, have really had the effect of making it less so.”

“We would not dare to conceive the things which are really mere commonplaces of existence.”

“Eschew the ordinary, disdain the commonplace. If you have a single-minded need for something, let it be the unusual, the esoteric, the bizarre, the unexpected.”

“There are strange red depths in the soul of the most commonplace man.”

“If a person would just make the effort, there's something to be learned from everything. From even the most ordinary, commonplace things, there's always something you can learn.”