This paper advances the debate over the question whether false beliefs may nevertheless have warrant, the property that yields knowledge when conjoined with true belief. The paper’s first main part—which spans Sections 2–4—assesses the best argument for Warrant Infallibilism, the view that only true beliefs can have warrant. I show that this argument’s key premise conflicts with an extremely plausible claim about warrant. Sections 5–6 constitute the paper’s second main part. Section 5 presents an overlooked puzzle about warrant, and uses that puzzle to generate a new argument for Warrant Fallibilism, the view that false beliefs can have warrant. Section 6 evaluates this pro-Fallibilism argument, finding ultimately that it defeats itself in a surprising way. I conclude that neither Infallibilism nor Fallibilism should now constrain theorizing about warrant.