On the Logical Asymmetry of the Burden of Proof

The burden of proof is widely used in argumentation theory, philosophy of science, and legal reasoning, but its logical basis is often left unclear. It is commonly treated as a dialogical rule, a procedural convention, or a norm of fair debate. Such approaches explain how the burden of proof operates within particular contexts, but they do not explain why it must be allocated asymmetrically in the first place. This paper argues that the asymmetry follows from a simple logical relation between claims, independent of dialogical, procedural, or pragmatic considerations. When one claim is logically stronger than another—by entailing it without being entailed in return—it im- poses additional restrictions on what may be accepted. Accepting these restrictions without justification is therefore logically arbitrary. From this relation it follows that the burden of proof must rest on the logically stronger claim. This result is not proposed as a norm of debate or a procedural rule, but as a minimal logical constraint on non-arbitrary reasoning. Making this constraint explicit helps to clarify why disputes over the burden of proof recur across different domains and why attempts to reverse the burden typically lead to stalemate.