Form-Independence in the Sorites Paradox

While the Sorites paradox is often presented in a propositional conditional form, it can be recast using disjunctive, conjunctive, or modus tollens syllogism. This paper challenges Kit Fine’s claim that only the conjunctive form is motivated. All four propositional forms are effective because they express three deeper, first-order principles: (1) the familiar principle of Tolerance, (2) the often-implicit assumption of Monotonicity, and (3) a novel claim I call Local Interdefinability (LI). LI is the thesis – motivated by contextualist empirical observations and by the salience of vague contraries – that for adjacent members of a soritical series, vague contraries (such as “tall” and “short”) function as contradictories. LI lets the conjunctive form proceed without any explicit elimination of double negation. Moreover, Kit Fine’s case against the conditional form loses its force since LI covers the gap between the conjunctive and conditional forms, and his case against the disjunctive form is undermined by the rejection of Monotonicity. The paper concludes that the unity of the Sorites paradox lies above the propositional level.