Concept · Cognitive Bias: Formal logical fallacies
Non sequitur
Origin: Traditional Latin rhetoric
Biological Parallel
'Peacock tails are costly. Therefore, they signal health.' This seems to follow but doesn't—costliness alone doesn't guarantee honest signaling. The tail could be: arbitrary fashion (runaway selection), manipulation, or frozen historical accident. The non sequitur: assume functional explanation when evolutionary process could be non-adaptive. Gould's spandrels critique was precisely this—architectures have features that don't follow from function. Not everything is adaptive just because it's visible.