Peter Bevelin: A Few Lessons From Sherlock Holmes

Peter Bevelin‘s first book, Seeking Wisdom from Darwin to Munger, is one of the best books you’ve probably never heard of. He’s just released another book, A Few Lessons from Sherlock Holmes (Kindle), aimed at those who want to improve their thinking.

“Peter Bevelin is one of the wisest people on the planet.”

— Nassim Taleb

I’m a big fan of Sherlock Holmes, and Peter is not the first person to explore the wisdom that can be drawn. Maria Konnikova’s book, Mastermind: How To Think Like Sherlock Holmes, takes a deep look at Sherlock Holmes’s methodology to develop the habits of mind that will allow us to mindfully engage the world.

Peter’s book is shorter than Maria’s and encourages you to draw your own conclusions. He’s distilled Arthur Conan Doyle’s famous detective Sherlock Holmes into principles and quotes.

This book will appeal to both Sherlock fans as well as those who want to think better. It contains useful and timeless methods and questions applicable to a variety of important issues in life and business. We could all benefit from A few lessons from Sherlock Holmes.

Let’s look at some of the lessons Bevelin brings to our attention.

“What distinguishes Holmes from most mortals,” Bevelin writes, “is that he knows where to look and what questions to ask. He pays attention to the important things, and he knows where to find them.”

Many ideas over a wide range of disciplines help us gain perspective (queue mental models).

Breadth of view, my dear Mr. Mac, is one of the essentials of our profession. The interplay of ideas and the oblique uses of knowledge are often of extraordinary interest.(Holmes; The Valley of Fear)

The Memory Attic

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. (Holmes; A Study in Scarlet)

So says the statistician.

You can, for example, never foretell what any one man will do, but you can say with precision what an average number will be up to. Individuals vary, but percentages remain constant. (Holmes; The Sign of the Fear)

Knowledge Doesn’t Make us Wise

One of the best things about Peter is how he adds outsiders to the mix. He inserts this quote from Montaigne:

Judgment can do without knowledge but not knowledge without judgment. (Montaigne)

Never jump to conclusions.

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. (Holmes; Wisteria Lodge)

Don’t theorize before data.

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. (Holmes; A Scandal in Bohemia)

Make sure the facts are facts.

I realize that if you ask people to account for “facts”, they usually spend more time finding reasons for them than finding out whether they are true. … They skip over the facts but carefully deduce inferences. They normally begin thus: “How does this come about?” But does it do so? That is what they ought to be asking. (Montaigne)

See the Forest

The principal difficulty in your case … lay in the fact of there being too much evidence. What was vital was overlaid and hidden by what was irrelevant. Of all the facts which were presented to us we had to pick just those which we deemed to be essential, and then piece them together in their order, so as to reconstruct this very remarkable chain of events. (Holmes; The Naval Treaty)

Small things may be important.

The smallest point may be the most essential. (Holmes; A Study in Scarlet)

We see but don’t Observe

What we see is all we think is there — What often leads us astray in an investigation is that we adopt the theory which is most likely to account for the “visible” and found facts but what if the important is left out? What is not reported, withheld, hidden?

Take time to think things over.

Sherlock Holmes was a man … who, when he had an unsolved problem upon his mind, would go for days, and even for a week, without rest, turning it over, rearranging his facts, looking at it from every point of view until he had either fathomed it or convinced himself that his data were insufficient. (Dr. Watson; The Man with the Twisted Lip)


Peter’s books tend to become very hard to find a few months after they are released. Used editions often sell well above cover price, so if you’re interested, I encourage you to order A Few Lessons From Sherlock Holmes today.