Non sequitur

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Non sequitur (Latin: "It does not follow") is a logical fallacy that involves arguing from a premise to a conclusion with a lack of sufficient connection between the two.[1]


Classically, the term non sequitur applies to:

  1. A conclusion that does not follow from the premises or evidence.[2]
  2. A statement that does not necessarily follow from preceding statements.[2]

Some authorities use the term non sequitur to refer generally to any fallacy involving the introduction of irrelevant considerations.[3] This, then, would include ad hominem and special pleading.


The most common example of non sequitur is any attempt to infer causation from correlation alone. An argument of causality—that is, that X caused Y--is always subject to weakening if one can show that:

  1. Y could have occurred with or without X.
  2. Another event, Z, could have caused Y.
  3. Y caused X rather than X causing Y.

The usual way to weaken a non sequitur is simply to show that two facts, that might happen to correlate, are in fact not mutually relevant. Of course, showing that the chain of implication is reversed—meaning that the first named fact actually follows from the second, rather than the second from the first—will cast even more serious doubt on the argument.


  1. Glenn Whitman, Non sequitur, Glen Whitman's Debate Page, August 30, 2005. Retrieved April 9, 2007.
  2. 2.0 2.1 Definition of non sequitur in The American Heritage® Dictionary of the English Language, 4th. ed., Houghton Mifflin Company, 2006. Retrieved April 9, 2007.
  3. Paul Raveling, Non sequitur logical fallacies at Retrieved April 9, 2007.