A Few Lessons from Sherlock Holmes

It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.

Before turning to those moral and mental aspects of the matter which present the greatest difficulties, let the inquirer begin by mastering more elementary problems. Let him on meeting a fellow-mortal, learn at a glance to distinguish the history of the man and the trade or profession to which he belongs. Puerile as such an exercise may seem, it sh

Common diseases cause uncommon symptoms more often than uncommon diseases cause common symptoms. (Medical maxim)

Which is the simplest, most natural explanation - the one requiring the least assumptions needed to explain the facts? There never was a sounder logical maxim of scientific procedure than Ockham’s razor...before you try a complicated hypothesis, you should make quite sure that no simplification of it will explain the facts equally well.

Patterns repeat but not always - Is it the same situation or circumstances or is it unique and fundamentally different from the past - what factors, conditions, behavior differ? Was it a random factor? We ought not to be ignorant that the same remedies are not good for all. (Celsus) But remember that we see what we are looking for - if we look for

“You appeared to read a good deal upon her which was quite invisible to me,” I remarked. “Not invisible but unnoticed, Watson. You did not know where to look, and so you missed all that was important.” (Holmes; A Case of Identity) Yes indeed you see, we all see, but often you do not observe. (Joseph Bell, Dr. Joe Bell) “You see, but you do not obse

The fatal mistake which the ordinary policeman make is this, that he gets his theory first, and then makes the facts fit it, instead of getting his facts first and making all his little observations and deductions until he is driven irresistibly by them into an elucidation in a direction he may never have originally contemplated.

Criticize ourselves - Have we tried to find evidence against what we believe? Why might we be wrong? What have we overlooked? What (new) information or evidence is needed to make us change our mind? When we meet a fact which contradicts a prevailing theory, we must accept the fact and abandon the theory, even when the theory is supported by great n

My dear Watson, you as a medical man are continually gaining light as to the tendencies of a child by the study of the parents. Don’t you see that the converse is equally valid? I have frequently gained my first real insight into the character of parents by studying their children.