Xiaoyang Yu

Eddy Keming Chen argues in "The Simplicity of Physical Laws" (*Noûs*, 2025) that "simplicity is a fundamental epistemic guide to lawhood. Roughly speaking, simpler candidates are more likely to be laws, all else being equal." This paper reveals this principle faces a **fundamental dilemma**. Core argument: When two candidate theories are empirically equivalent, they either (A) differ only in expressive form, or (B) differ in ontological commitments (what entities they posit). In case A, simplicity is merely expressive preference, and there is no question of "which is more likely to be a law"; in case B, choosing one based on simplicity is unreasonable bias, because we cannot judge which ontological commitment is more correct. In either case, simplicity cannot serve as the "epistemological guide" Chen claims. This paper further argues that Chen confuses "empirical equivalence" with "complete equivalence," mistakenly believing theories with identical empirical predictions have "all else equal"—but if ontological commitments differ, "all else" is fundamentally unequal, and simplicity has no epistemological authority. This reveals deep tension between positivism and realism: if one insists on realism (ontological differences are real), one cannot appeal to simplicity; if one appeals to simplicity, one must abandon realism (acknowledging ontological differences are meaningless).