We’ve talked about how thinking in a mutually exclusive and collective exhaustive way is central to effective problem solving. But this is such an important concept that we should talk about it more.

First, be CEME, not MECE

To solve a problem in a MECE way you need to consider all possible solutions exactly once. To do that, it is usually simpler to first think about all possible solutions and then to arrange them so that you only consider them once. So it’s really about being CEME rather than MECE.

The collective exhaustive part is about creative thinking, it’s about innovative thinking, diverging. It’s about the big picture, including everything. You are thinking about “else”, as in: “what else could be the source of my problem?” or “what else could be a potential solution for my problem”.

The mutually exclusive part is about critical thinking, arranging bits, synthesizing, converging. It’s about organizing information—root causes or potential solutions—in your issue tree so that you only consider it once. Organizing usually works best when you already have some matter to arrange, as opposed to thinking out of thin air about possible categories and then populating them.

To be clear, thinking in a MECE way usually is an iterative process that alternates diverging and converging thinking patterns. But it makes better sense to start with the diverging part before converging.

Perhaps a helpful analogy is thinking about how to draw a complex subject, such as a human face. We each do it differently, but if you aren’t an expert, chances are that you’ll first go with a top-down approach: setting up the general shape of the face, placing the important features—the eyes, the nose, the mouth—and stepping back to ensure that it is consistent with your mental or physical model. Once everything seems to be more or less in place, you can focus on the details: such as adding the shading to the eyes that will create the right impression. But there is no point starting with drawing the eyes and mouth in extensive detail just to step back and find out that they are in the wrong place. Even Picasso did it that way. Well, in all fairness, he probably could have started drawing his bull by drawing the eye and the horns—and they would have been perfectly placed—but, well, he is Picasso.

Second, it’s not really about being mutually exclusive

MECE thinking in business problem solving is a misnomer, firmly ingrained in the community courtesy of [insert-here-the-name-of-whichever-major-consultancy–you–prefer] (it doesn’t matter because they all do it). The fact is, we are not really looking for mutual exclusiveness of solutions. Let me explain.

In the strict sense, two events are mutually exclusive if the occurrence of one precludes the occurrence of the other (source). The key word here is “precludes”. We aren’t interested in events that preclude others from occurring—otherwise, we would be preventing ourselves from following potentially viable options. What we are interested in is independent events: ones that you can pursue individually.

Sometimes, you’ll be able to pursue several options at the same time: for instance, you’ll be able to boost profitability by acquiring more clients and reducing your variable costs. Some other times, pursuing one solution will preclude you from pursuing another: if you’re traveling from New York City to London by plane, you can’t do it by boat. But whether independent solutions are also mutually exclusive depends on the nature of the problem or the nature of the solution.

Even in a specific problem, you may have solutions that will prevent you from pursuing any other—for instance because they are so time consuming—and solutions that will allow you to consider others. But this consideration comes later in your problem-solving process, when you are electing the solution(s) that you want to pursue.

When organizing solutions, you really are looking at doing so in independent branches, no ME exclusive ones.

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