I read A Few Lessons from Sherlock Holmes by Peter Bevlin. It's a really fun read, a collection of quotes from Holmes stories with life lessons that are full of wisdom.
Here are ten things I learned (all direct quotes from the book).
1. Approach problems with a blank mind:
We approached the case... with an absolutely blank mind, which is always an advantage. We had formed no theories. We were there simply to observe and to draw inferences from our observations. ... I have not all my facts yet, but I do not think there are any insuperable difficulties. Still, it is an error to argue in front of your data. You find yourself insensibly twisting them round to fit your theories. ... 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.
2. Take a multidisciplinary approach to learning:
Considering many ideas over a wide range of disciplines give us perspective and help us consider the big picture or many aspects of an issue. Breadth of view... is one of the essentials of our profession. The interplay of ideas and the oblique uses of knowledge are often of extraordinary interest. ... One's ideas must be as broad as Nature if they are to interpret Nature. All other men are specialists, but his specialism is omniscience.
3. Be selective about what you believe:
I consider that a man's brain originally is like a little empty attic, and you have to stock it with such furniture as you choose. A fool takes in all the lumber of every sort that he comes across, so that the knowledge which might be useful to him gets crowded out, or at best is jumbled up with a lot of other things so that he has a difficulty in laying his hands upon it. ... Now the skillful workman is very careful indeed as to what he takes into his brain-attic. He will have nothing but the tools which may help him in doing his work, but of these he has a large assortment, and all in the most perfect order. It is a mistake to think that that little room has elastic walls and can distend to any extent. Depend upon it there comes a time when for every addition of knowledge you forget something that you knew before. It is of the highest importance, therefore, not to have useless facts elbowing out the useful ones.
4. It is so tempting to fool yourself:
The greatest sign of an ill-regulated mind is to believe things because you wish them to be so.
5. Ensure you aren't blinded by your discoveries:
But some of us are too much attracted by the thought of rare things and forget the law of averages in diagnosis. There is a man who is very proud of having diagnosed a rare abdominal disease on several occasions. But as for some years he made this diagnosis in every obscure abdominal condition, of course being nearly always wrong one cannot feel that he deserves much credit.
6. Knowledge and education can backfire:
Perhaps, when a man has special knowledge and special powers like my own, it rather encourages him to seek a complex explanation when a simpler one is at hand.
7. You have to tame and filter your own ideas:
Nothing can be done without preconceived ideas; only there must be the wisdom not to accept their deductions beyond what experiments confirm.
8. Simple problems can be the hardest to solve:
Paradoxically the strange crime is often easier to solve than the common one. I have already explained to you that what is out of the common is usually a guide rather than a hindrance. ... It is only the colourless, uneventful case which is hopeless. ... It seems, from what I gather, to be one of those simple cases which are so extremely difficult. That sounds a little paradoxical. But it is profoundly true. Singularity is almost invariably a clue. The more featureless and commonplace a crime is, the more difficult it is to bring it home.
9. Data can increase confidence faster than ability:
More information isn't necessarily better information but it may falsely increase our confidence. What is not worth knowing is not worth knowing. A wise man sees as much as he ought, not as much as he can.
The world is full of obvious things which nobody by any chance ever observes.