Ambiguous middle term
Origin: Traditional syllogistic logic
Biological Parallel
Ambiguous terms create logical traps when meaning shifts mid-argument. Evolutionary biology's classic: 'Successful organisms are adapted. Adapted organisms survive. Therefore, successful organisms survive.' Circular—'adapted' means survival-outcome in premise one, trait-property in premise two. Philosophers document this as natural selection's tautology problem; 'fitness' slides between 'reproductive success' (outcome) and 'traits conferring advantage' (property). The middle term shifted. Biology weaponizes this. Scarlet kingsnakes mimic coral snakes in Batesian deception: 'similar' patterns (visual resemblance) exploit predators assuming 'similar' chemistry (toxicity). Innate avoidance documented in motmots—birds avoid red-yellow patterns without prior exposure. But similarity is visual only; kingsnakes lack venom. The middle term 'similar' shifts from appearance to biochemistry. Cryptic species reverse the trap: 25 mouse lemur species once classified as one (M. murinus) because morphological 'identity' was mistaken for genetic identity. The term 'species' shifted from morphological to genetic definition. In business strategy, 'success' slides between market share (outcome) and competitive advantage (property). Survivor bias creates tautology: 'successful companies adapted' is circular when 'adapted' means 'survived.' Ambiguous middles make tautologies look like explanations.