Historically, the most persuasive argument against external reasons proceeds through a rationalist restriction: For all agents A, and all actions Φ, there is a reason for A to Φ only if Φing is rationally accessible from A’s actual motivational states. Here I distinguish conceptions of rationality, show which one the internalist must rely on to argue against external reasons, and argue that a rationalist restriction that features that conception of rationality is extremely implausible. Other conceptions of rationality can render the restriction true, but then the restriction simply fails to rule out external reasons.