Reaching Down the Rabbit Hole: Extraordinary Journeys into the Human Brain

by Allan H. Ropper

The Holmesian thrill lies in instantly seizing on the right explanation from the barest facts. What Holmes should be doing, and what Dr. Watson usually suggests, is exploring other possible explanations. Instead of assuming that he’s always right, Watson might say, “Just this once, consider the possibility that you might be wrong.”

Deductive reasoning, as opposed to inductive reasoning, is what detectives and diagnosticians should be doing. Deduction works from general facts toward specific conclusions. If the “facts” really are facts, the conclusions have to be true. But induction—a quicker and much more practical method of reasoning that everyone uses every day—can lead to errors. That’s because an inductive process infers a conclusion, but doesn’t prove it.