Sherlock Holmes' Problem-Solving Formula
October 26, 2010
What's the best way to solve a problem? One approach, based on the logic used by Sherlock Holmes, can deliver significant results, according to the following excerpt from Gregg Young's new book Reasoning Backwards: Sherlock Holmes' Guide to Effective Problem Solving. Book excerpt republished here with the permission of Gregg Young. Solving problems is detective work. The search for the root causes of a problem is very much like the search for the perpetrator of a crime, so Sherlock Holmes' perspective is insightful. The following excerpts from The Complete Sherlock Holmes by Sir Arthur Conan Doyle provide the framework for an effective investigation:
In solving a problem of this sort, the grand thing is to be able to reason backwards. That is a very useful accomplishment, and a very easy one, but people do not practice it much. In the everyday affairs of life, it is more useful to reason forwards, and so the other comes to be neglected. There are fifty who can reason synthetically for one who can reason analytically.This quotation is the fundamental concept all effective problem solvers use. Everything derives from it. Synthetic thought, the way we live life everyday, uses divergent thinking. It flows from Cause to Effect. It generates a variety of possible options, and then decides which ones to pursue. During problem solving, synthetic thinking is only appropriate when developing possible solutions to implement after the searcher has identified the root causes. Synthetic thinking is inappropriate when searching for root causes because the root causes already exist and simply need to be discovered. Synthetic divergent thinking is ineffective because it guesses about root causes rather than systematically searching for them. Analytical thought, reasoning backwards, is convergent thinking. It proceeds from Effect to Cause. It is the superior approach for identifying root causes because it quickly leads to complete solutions. Analytical thinkers systematically look for the clues that will reveal the root causes. They use observation followed by deduction. The techniques in this book have helped thousands of people to apply this principle and become effective problem solvers.
Always approach a case with an absolutely blank mind. Form no theories, just simply observe and draw inferences from your observations.These three comments provide a closer look at the process and the contrast between the more common synthetic approach and Holmes' analytical approach. Today's most common problem solving techniques call for people to begin by asking, "What COULD BE the root causes?" These methods make the mistake of encouraging problem solvers to brainstorm (hypothesize, guess, speculate, imagine...) dozens to hundreds of possible root causes before they gather any data. People invariably pursue many wrong choices before finding an actual root cause. This is slow, and it introduces bias to the process because the investigator is testing someone's theory. People who begin by brainstorming rarely develop complete solutions because they rarely persevere to find all the root causes. Sherlock Holmes' approach asks, "What IS different when problems occur?" This leads to observation, followed by deduction. Observing with a blank mind eliminates all the shortcomings inherent to brainstorming. Observation simply allows the activity to present the clues that point to the root causes. It might seem on the surface that Holmes' rejection of theory formation (i.e., hypotheses) before data collection is in conflict with the Scientific Method, but it is not. The basic outline of the Scientific Method is:
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.
I never guess. It is a shocking habit destructive to the logical faculty.
- State the Problem.
- Conduct Research.
- Formulate Hypotheses.
- Test the Hypotheses.
- Confirm Hypotheses or Formulate New Hypotheses.
Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth.This last Holmes quotation provides one last guideline. By looking for clues, the problem solver eliminates the factors that are not involved, "the impossible". Whatever is left will be the root causes, however improbable they might seem. This introduces a second weakness of divergent thinking. In many cases, the actual root cause is something no problem solver would ever have come up with as a potential factor much less put any time or effort into investigating. Sherlock Holmes used a simple, three-step method to solve crimes: Observation, Deduction, Knowledge. Effective problem solvers use the same approach. They observe carefully to discover any clues that eliminate the impossible, so they can deduce the causes and implement solutions. The guidelines for Holmes' approach to problem solving:
- Never hypothesize root causes of problems. Use convergence tools to non-invasively observe the activity and identify the critical factors, the root causes of the problem.
- If an activity usually works well, but occasionally generates bad outcomes, it is fundamentally sound. When it creates good outcomes, every condition is set correctly. Whenever it creates bad outcomes, some condition or conditions have changed.
- No more than 3 critical factors are responsible for 90-100% of all bad outcomes.
- One factor is always responsible for at least 50% of bad outcomes.
- Compare performance extremes to discover patterns and consistent differences, which always relate to the 1-3 critical factors.
- The solution is tighter control of the critical factors.