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Non Sequitur

(also known as: derailment, “that does not follow”, irrelevant reason, invalid inference, non-support, argument by scenario [form of], false premise [form of], questionable premise [form of], non-sequitur)

Description: When the conclusion does not follow from the premises.  In more informal reasoning, it can be when what is presented as evidence or reason is irrelevant or adds very little support to the conclusion.

Logical Form:

Claim A is made.

Evidence is presented for claim A.

Therefore, claim C is true.

Example #1:

People generally like to walk on the beach.  Beaches have sand.  Therefore, having sand floors in homes would be a great idea!

Explanation: As cool as the idea of sand floors might sound, the conclusion does not follow from the premises.  The fact that people generally like to walk on sand does not mean that they want sand in their homes, just like because people generally like to swim, they shouldn’t flood their houses.

Example #2:

Buddy Burger has the greatest food in town.  Buddy Burger was voted #1 by the local paper.  Therefore, Phil, the owner of Buddy Burger, should run for president of the United States.

Explanation: I bet Phil makes one heck of a burger, but it does not follow that he should be president.

Exception: There really are no exceptions to this rule. Any good argument must have a conclusion that follows from the premises.

Tip: One of the best ways to expose non sequiturs is by constructing a valid analogy that exposes the absurdity in the argument.

Variations: There are many forms of non sequiturs including argument by scenario, where an irrelevant scenario is given in an attempt to support the conclusion.  Other forms use different rhetorical devices that are irrelevant to the conclusion.

False or questionable premises could be seen as errors in facts, but they can also lead to the conclusion not following, so just keep that in mind, as well.

References:

Hyslop, J. H. (1892). The Elements of Logic, Theoretical and Practical. C. Scribner’s Sons.



Registered User Comments

Jason Mathias
Monday, April 30, 2018 - 08:51:33 AM
Is this a non sequitur?
Joe- 99% of climate sciences worldwide accept the fact of anthropogenic climate change.

Jill- Well here is a paper written by a scientist that doubts anthropogenic climate change. Therefor anthropogenic climate change is just natural cycles and not man made.

Joe- I know there are a small handful of published papers denying anthropomorphized climate change. But there are millions supporting it. If I gave you a lottery number that had a 1% chance of winning, vs a number that had a 99% chance of winning, you'd pick the one that had the 99% chance of winning because its way more probable if not basically certain. The only reason you'd cling to the 1% is if you had a bias or agenda to uphold.

Jill- So years ago in class I took an exam and the entire class failed but I was the only who passed. By your logic this couldn't be because the 99% has to be right and the 1% can't possibly be.This debate is getting old. Your stuck with your belief so good for you. By the way smart guy learn how the science community works before you go attempting to correct someone about a subject matter you know very little about. When scientist are funded they will not publish papers going against who is funding them. That is a fact.

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Bo Bennett, PhD
Monday, April 30, 2018 - 08:59:38 AM
I see no non-sequitur. Joe is deferring to an overwhelming scientific consensus on a scientific issue. Perfectly reasonable. Jill is reasoning inconsistently because she is ignoring her own argument—the many studies on climate change funded by organizations who have a financial interest is ignoring climate change.

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Jason Mathias
Monday, April 30, 2018 - 09:20:17 AM
@Bo Bennett, PhD: What fallacy would the, "So years ago in class I took an exam and the entire class failed but I was the only who passed. By your logic this couldn't be because the 99% has to be right and the 1% can't possibly be." be?

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Bo Bennett, PhD
Monday, April 30, 2018 - 10:42:23 AM
@Jason Mathias : Strawman. Joe did not make that claim.

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Krista Neckles
Saturday, March 17, 2018 - 11:42:15 AM
Dear Sir,

Would enthymemes(arguments with a missing premise or conclusion) be an example of a non-sequtur? The reason I ask this is because I think that sometimes if one omits a point, then it may not be apparent how the conclusion follows from a premise.

Thank you Sir.

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Bo Bennett, PhD
Sunday, March 18, 2018 - 03:43:58 PM
Possibly. I would have to see an example.

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Krista Neckles
Sunday, March 18, 2018 - 06:31:16 PM
@Bo Bennett, PhD: Thank you Sir. I read more material about enthymemes so I understand its use a bit better.

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Jason Mathias
Saturday, March 10, 2018 - 10:31:37 PM
Is this a non sequitur fallacy?
Science concludes evolution.
Creationism concludes God
Therefor science concludes God.

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Bo Bennett, PhD
Sunday, March 11, 2018 - 08:31:39 AM
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Jason Mathias
Sunday, March 11, 2018 - 09:10:01 AM
@Bo Bennett, PhD:
Ok thanks. Would this also apply to someone claiming that evolution isn't science. And that science proves DNA cant be by chance and was designed.

Science shows that DNA is designed
All things designed have a designer
Therefor God

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Bo Bennett, PhD
Sunday, March 11, 2018 - 09:12:11 AM
@Jason Mathias : Hard to tell just from the subject of the argument rather than the form. Sounds to me like just an claim without support.

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Jason Mathias
Friday, March 09, 2018 - 12:12:15 PM
Is this a non sequester fallacy:
1- Only intelligent human minds intentionally create complex things with purpose and intent.
2- The universe is a complex thing.
3- Therefor God is a human like being who created the universe with purpose and intent.

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Bo Bennett, PhD
Friday, March 09, 2018 - 02:10:43 PM
In that the conclusion does not follow, yes, a non-sequitur. Many problems with this.

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