Non Sequitur — When Logic Wears a Disguise
Non sequitur (Latin: 'it does not follow') is the broad formal fallacy in which the conclusion does not logically follow from the premises. While many specific fallacies are technically non sequiturs, the term is applied when the logical gap is stark and cannot be classified under a more specific fallacy category. The conclusion may be true or false independently, but the argument provides no valid logical path from premises to conclusion, and the disconnect is too fundamental to be attributed to a missing premise.
Also known as: Does Not Follow, Irrelevant Conclusion (broad sense)
How It Works
Humans are association machines — we readily connect ideas that co-occur in experience even when no logical relationship exists. The confident presentation of premises followed by a conclusion triggers an assumption of logical connection that may not exist.
A Classic Example
"She's an excellent mathematician, so she'll make a great manager." (Mathematical ability does not entail management ability without substantial additional premises.)
More Examples
A politician declares: 'I grew up in a small town and know what hard work means. Therefore, my tax policy is the right one for this country.' — Personal background has no logical connection to the correctness of a specific fiscal policy.
An ad campaign claims: 'Nine out of ten dentists recommend brushing twice a day. That's why you should trust our brand of running shoes.' — Dental professional endorsement of a hygiene habit has no bearing on the quality of athletic footwear.
Where You See This in the Wild
Ubiquitous in political speeches, advertising, everyday conversation, and social media posts where confident assertions substitute for logical argumentation. Also common in job interviews and performance reviews where irrelevant qualities are cited.
How to Spot and Counter It
Explicitly state what logical steps would be needed to get from the premises to the conclusion. If the gap cannot be bridged with reasonable assumptions, the argument is a non sequitur.
The Takeaway
The Non Sequitur is one of those reasoning errors that sounds perfectly logical at first glance. That's what makes it dangerous — it wears the costume of valid reasoning while smuggling in a broken conclusion. The best defense? Slow down and ask: does this conclusion actually follow from these premises, or am I just connecting dots that happen to be near each other?
Next time someone presents you with an argument that "just makes sense," check the structure. The feeling of logic is not the same as logic itself.