This post is part of a series on logical fallacies. For others in the series, check out the Logic and Argumentation section of our Resource Library.

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One year I was assigned to “teach” 3-year-old Sunday school at church. Teach is in quotation marks because I soon learned that not much real teaching is possible with that age group. My background had been in high school education, and, well, I was terrible with 3-year-olds.

It was a week before Easter Sunday, and I thought I might generate some interest with a simple question:

“Who knows what next Sunday is?” I asked.

Silence and wide-eyed stares.

“Come on. It’s a special day that we celebrate every year. Anyone?”

Finally, Andrew raised his hand. “Andrew! My man! What is next Sunday?”

With great confidence, Andrew said, “Proud.”

“That is an excellent example of a non sequitur, Andrew. Thank you.”

To this day, I don’t have the foggiest idea what Andrew was thinking. I can guess what character trait his parents were working on at the time, but how he got from Easter to pride, I’ll never know.

Non-sequitur is Latin for “it does not follow.” In everyday communication, it means a statement that is disconnected from the previous one. Like conversations I have with my wife when I’m not really paying attention (hypothetically, of course):

My wife: Honey, did you hear that Susan’s mother, Gabby, is expecting twins?

Me: I think I forgot to pay the gas bill this month.

In argumentation, however, non sequitur refers to a conclusion that cannot reasonably be deduced from the premises. It’s a broad, catch-all kind of term for a variety of specific logical fallacies. One example might be:

• Premise: All dogs are mammals.
• Premise: Cats are mammals.
• Conclusion: Therefore, cats are dogs.

The conclusion might even be true, but if it doesn’t logically follow from the premises, it’s still a non sequitur. A lucky guess, maybe, but a non sequitur:

• Premise: All U.S. Presidents are older than 35.
• Premise: Barack Obama is older than 35.
• Conclusion: Therefore, Barack Obama is a U.S. President.

I have illustrated this concept using syllogisms (a logical proposition expressed as two or more premises and a conclusion), but they are common in all kinds of everyday arguments and debates. All of the following are non sequiturs because the conclusion doesn’t follow logically from the previous statements.

• Global temperatures have been falling for more than a decade, so climate change is a hoax.
• Don’t hire that woman. Women’s IQs are lower than men’s and we need someone smart for this job.
• The Red Sox are the most talented team in baseball, so they are sure to win the World Series.
• If you are unhappy with the President’s policies, you must be a Republican.

Note that in these examples, it doesn’t matter whether the conclusion is true or not. The point is that they were determined in an illogical way. Even illogical or deceitful people are right sometimes (if you think a statement is wrong because an illogical or deceitful person said it, you have bought into the genetic fallacy).

In future posts, I’ll talk about some more specific kinds of non sequiturs, but it’s a good, broad term to understand.

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As always, I covet your comments.