Non Sequitur (Fallacy)

A non sequitur is a fallacy in which a conclusion does not follow logically from what preceded it. Also known as irrelevant reason and fallacy of the consequent.

As illustrated below, nonsequiturs are the products of many different kinds of errors in reasoning, including begging the question, false dilemma, ad hominem, the appeal to ignorance, and the straw man argument. Indeed, as Steve Hindes observes in Think for Yourself (2005), "A non sequitur is any pretended jump in logic that doesn't work cleanly, perhaps because of unfounded premises, unmentioned complicating factors, or alternative explanations, such as 'This war is righteous because we are French!' or 'You will do what I say because you are my wife!'"

The Latin expression non sequitur means "it does not follow."

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Definition and Examples of Conclusions in Arguments

By Richard Nordquist

Pronunciation: non SEK-wi-terr

Examples and Observations

Savannah City Manager Stephanie Cutter: We realize that it would be in the best interest of the community and our children to address the issue expeditiously. In order to make this happen, I respectfully request an eight-month payment delay calling for payment of the $10 million obligation on August 31, 2015.

John Llewellyn: Warming was caused by sunspots, or fluctuations in the Earth's orbit, or volcanic eruptions. Therefore it cannot be caused by mankind. The 'therefore' is the giveaway, the delicious non sequitur: just because Earth has warmed for one or another reason in the past is no reason why it cannot warm for a completely different reason in the future.

Justin E.H. Smith: Immanuel Kant, considered by many to be the greatest philosopher of the modern period, would manage to let slip what is surely the greatest non-sequitur in the history of philosophy: describing a report of something seemingly intelligent that had once been said by an African, Kant dismisses it on the grounds that 'this fellow was quite black from head to toe, a clear proof that what he said was stupid.'

Nigel Warburton: Non sequiturs are most obvious when absurd. For instance, from the facts that most cats like milk and some cats have tails I could not derive the conclusion that David Hume was the greatest British philosopher. That would be a complete non sequitur that borders on the surreal, whether or not its conclusion is true. Non sequiturs are often advertised by the spurious use of 'so' and 'therefore'..., but the context of a statement can also suggest that it is a conclusion derived from what has gone before even when there is no such word used to indicate it.
"Any formal fallacy will have a non sequitur as its conclusion, though most of these non sequiturs will be less obvious than the one above.

Bill Bryson: Non sequiturs are most often encountered in newspapers, where constructions such as the following are common: 'Slim, of medium height, and with sharp features, Mr. Smith's technical skills are combined with strong leadership qualities' (New York Times). What, we might ask, do Mr. Smith's height and features have to do with his leadership qualities?

Mabel Lewis Sahakian: The difference between the post hoc and the non sequitur fallacies is that, whereas the post hoc fallacy is due to lack of a causal connection, in the non sequitur fallacy, the error is due to lack of a logical connection.