2015.104: What Common Sense Is

The great thing about having blogged for more than eight years (eleven, if you count my first shortlived attempt) is that I have a record of my own increasing understanding of my subject.

I wrote in 2010 about fighting back against common sense—preempting and responding to the State’s argument that a jury should find a defendant guilty because of “common sense”:

“Common sense” has nothing to do with it. The words do not appear in a Texas criminal jury charge. The existence of jury trials is not common sense. The presumption of innocence is not common sense. Requiring proof beyond a reasonable doubt is not common sense.

What I didn’t have in 2010 was an explanation of what common sense is, until I saw this:

Screenshot of part of Scott Adams List of Cognitive Biases.

Screenshot of part of Scott Adams List of Cognitive Biases.

I knew about cognitive biases, of course, and about how they short-circuit rationality without our knowing it, but I had never made the connection before: “common sense” is just a polite term for our complex of cognitive biases.

In our everyday existences common sense gives us shortcuts so that we don’t spend a lot of time thinking our way through the same or similar problems time and again.1 Common sense is not appropriate in the jury room, though, because the problems faced by jurors are not similar to problems they have solved before.

Jury room problems may appear to be similar to real-world problems—common sense justifying itself—but the rules that apply in the jury room are different than those anywhere else. “Use your common sense” is a call to set aside those rules and decide the case based on cognitive biases.

In light of that and my developing unified theory of the criminal jury trial, I’ve changed my view of common sense.2 Instead of fighting it, own it.There are words that slip past our critical faculties and cause us to do things for reasons we cannot explain. For example, “because”: when you tell someone to do something because reason, he is more likely to do it than when you just tell him to do it. This is true regardless of the reason. Library patrons in line at a photocopier were much more likely to let someone cut in line to make a few copies if they were asked,

“Excuse me, I have 5  pages. May I use the Xerox machine, because I have to make copies?”

than if they were asked,

“Excuse me, I have 5  pages. May I use the Xerox machine?”3

Like “because” or “loophole,”4 the phrase “common sense” seems to cause suggestions to slip by people’s critical faculties. Given this fascinating fact, we trial lawyers can rage against the neurological machine, or we can use it to our clients’ advantage.Or we can do both.

  1. Those of you familiar with Richard Bandler and John Grinder’s “meta-model”  might think about whether any given cognitive bias represents generalization, distortion, or deletion. 

  2. The unfortunate thing about having blogged for more than eight years is that everyone else has a record of how little I understood eight years ago. 

  3. The same tendency did not obtain if the number of pages was 20 rather than five. 

  4. When a politician describes something as a “loophole,” you’re about to lose some freedom and he’s about to gain power. 


  1. Thanks, this is a great Hannukah and Christmas present. My brain knew this “common sense” argument was bologna from the persecutors, but your call to analyze that, as well as to own it, is very helpful. Hey, we can always learn from another perspective. Anna

  2. I don’t see “because I have to make copies” as offering any sort of reason. It may be attached to “because” but it is just repeating what needs to be done rather than providing any independent input.

  3. Cognitive biases by definition result in illogical thinking*. Not all common sense is illogical, however. For example, it is common sense to avoid closing your eyes at a crosswalk and stepping out into traffic hoping for the best. So isn’t it more accurate to say common sense often unfortunately includes cognitive biases, and it is that subset of common sense that you want to keep out of the jury room?

    I suggest a better definition of common sense is a collection of cognitive shortcuts thought to be accepted by the majority of a group.

    *Perhaps, though, you are just using a looser definition of cognitive bias to include both rational and irrational shortcuts.

    1. I reject your common-sense definition. think you may be confusing process with result.

      Common sense and cognitive biases are irrational processes—”cognitive shortcuts”—that often but incidentally lead to correct results in the world outside the jury room.

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