Circumstantial evidence is a very tricky thing. It may seem to point very straight to one thing, but if you shift your own point of view a little, you may find it pointing in an equally uncompromising manner to something entirely different

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

So swift, silent and furtive were his movements like those of a trained bloodhound picking out a scent, that I could not but think what a terrible criminal he would have made had he turned his energy and sagacity against the law instead of exerting them in its defense. -Dr. Watson, The Sign of the Four

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.

When you have eliminated the impossible, what is left, no matter how unlikely, is the truth.

A fine thought in fine language is a most precious jewel, and should not be hid away, but be exposed for use and ornament.

One dumb-bell, Watson! Consider an athlete with one dumb-bell. Picture to yourself the unilateral development - the imminent danger of a spinal curvature. Shocking, Watson, shocking!