insequitur

Insequitur is a Latin term occasionally found in discussions of logic and rhetoric. It denotes an inference whose conclusion does not follow from the premises, effectively the Latin counterpart of the English term non sequitur. In scholastic and rhetorical writings, insequitur was used as a label or marginal note to flag a faulty step in an argument rather than to provide a full critique.

Etymology and usage: The word derives from the Latin verb sequi “to follow” and the form sequitur “it follows.” In some sources, insequitur is used to express a negative consequence or lack of logical connection, though modern usage overwhelmingly prefers non sequitur for this idea. Because Latin manuscripts vary, insequitur may appear in translations or discussions of classical logic as an archaism or illustrative example rather than as a standard technical term.

Examples: A typical insequitur would be an inference that asserts something unrelated to the premises. For example: Premise 1: All dogs are mammals. Premise 2: This animal is a mammal. Conclusion: Therefore, this animal is a dog. The conclusion does not logically follow from the premises, illustrating a non sequitur, labeled insequitur in some historical texts.

Relation to non sequitur: Non sequitur is the modern, widely used term in logic and philosophy. Insequitur remains a historical or linguistic reference, encountered mainly in studies of rhetoric, Latin texts, or discussions of fallacies in tradition.