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McNamara Fallacy

(also known as: quantitative fallacy, Skittles fallacy)

Description: When a decision is based solely on quantitative observations (i.e., metrics, hard data, statistics) and all qualitative factors are ignored.

Logical Form:

Measure whatever can be easily measured.
Disregard that which cannot be measured easily.
Presume that which cannot be measured easily is not important.
Presume that which cannot be measured easily does not exist.

Example #1:

Donald Trump Jr. Tweeted:

If I had a bowl of skittles and I told you just three would kill you. Would you take a handful? That's our Syrian refugee problem.

Explanation: Let's ignore the gross statistical inaccuracy of this quote for a moment (i.e., 1 out of every 100 or so Syrian refugees is not going to kill you). The actual quantitative data about how many Syrian refugees are likely to be terrorists is some number greater than zero. The downside of letting Syrian refugees in the U.S. can be measured quantitatively, perhaps your risk of getting killed by a terrorist will increase from 3.46 billion to one to 3.4 billion to one. The upside, for the most part, is qualitative, that is, cannot be measured easily. What is a human life worth? How do we measure the suffering of others? Since these cannot easily be measured, we ignore them and conclude that taking in Syrian refugees is a bad decision.

Example #2:

The numbers on gun violence speak for themselves. We should ban guns in the country!

Explanation: While the numbers on gun violence are alarming, we can't ignore the qualitative benefits of gun ownership such as the right to own a weapon and personal safety. When making a decision, all factors need to be considered, even if they cannot be measured quantitatively.

Exception: It is possible that certain decisions do not have any qualitative components, or the qualitative components are irrelevant. For example, very often salespeople or high-end stores will attempt to sell us overpriced products or services that we can get elsewhere for 1/2 the price. They might justify their higher prices with "service," where nobody needs "service" when buying toilet paper.

Tip: Qualitative factors are often measured with a degree of subjectivity, meaning that one might give different moral weight to an idea based on one's core values. Consider this before being too harsh in your judgment of others' political or religious views.


Fischer, D. H. (1970). Historian’s Fallacies. Harper Collins.

Registered User Comments

Krista Neckles
Monday, May 21, 2018 - 04:04:14 PM
Hello Sir,

What if you acknowledge that qualitative factors matter but that there are not as important as quantiative factors?

Would this line of thought still be a fallacy?

Thank you

Krista Neckles

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Bo Bennett, PhD
Monday, May 21, 2018 - 05:10:06 PM
Depending on how the acknowledgement is phrases, I would probably say that it wasn't a problem.

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Krista Neckles
Sunday, April 29, 2018 - 04:36:58 PM
Hello again Sir,

I am thinking of a few examples of this fallacy. Can you tell me if this fallacy in question has been committed?

1) Suppose somebody believes that in school earning the highest grades is most important even at the expense of mental health. But can't one measure the state of someone's mental health?
2) Dismissing the symbolism of a story as unimportant and instead only focusing on the plot of the story
3) My sister's mug that she bought during an excursion she enjoyed very much was thrown out. I though that buying another mug would make her happy but it would not

Also would the fallacy of tokenism be committed if the arguer only focuses on the qualitative aspects?

Thank you Sir,

Krista Neckles

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