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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. 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.

References:

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



Registered User Comments

S Ellison
Friday, November 02, 2018 - 07:05:43 PM
You might want to look again at Example 2. The right to own a gun is not a benefit of gun ownership; the possibility of gun ownwership is (debatably) a consequence of the right to bear arms.
You should also look at the assertion that personal safety is a benefit. Since a very large proportion of gun deaths are suicides using ones’s own weapon or a household firearm, murder with a household firearm, or accident, the evidence is that personal safety in general is reduced by gun ownership. The benefit is specifically self-defence, not personal safety. Of course, outside the police and armed forces, instances of effective self defence with a firearm are far less frequent than suicides, murder etc, so the net societal benefit is negative; but that does not of itself undermine the fact that self defence is a benefit of firearm ownwership for an individual.

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Bo Bennett, PhD
Friday, November 02, 2018 - 07:15:18 PM
I just removed the named benefits. These are not important for the point of the example.

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David Salzillo Jr.
Thursday, July 12, 2018 - 01:02:07 PM
Why is this called the McNamara Fallacy? Does it have to do with a member of the Johnson administration? Just curious.

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Bo Bennett, PhD
Thursday, July 12, 2018 - 02:09:26 PM
Named for Robert McNamara, the United States Secretary of Defense from 1961 to 1968. Just like diseases, you don't want fallacies named after you!

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David Salzillo Jr.
Friday, July 13, 2018 - 02:27:14 PM
@Bo Bennett
Why was it named after him?

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Bo Bennett, PhD
Friday, July 13, 2018 - 02:59:28 PM
@David Salzillo Jr.: Not sure. Check wiki... might find something there.

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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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