Abstract: This paper discusses the function and scope of incompatibilist or transcendental freedom in Kant's moral philosophy. The prevailing view among scholars, most notably Allison, is that the function of transcendental freedom is to enable us to articulate a first-person conception of ourselves as rational agents involved in deliberation and choice. Thus, the scope of transcendental freedom is rational agency in general. In order to perform this function, freedom has to be merely conceivable. Pace Allison, I argue that our first-person conception is neutral with respect to causal determinism, and that the function of transcendental freedom is to provide the metaphysical conditions of the possibility of genuine moral responsibility and perfect justice, and to get rid of moral luck. In order to perform this function, transcendental freedom has to be not just conceivable, but metaphysically real. My view suggests that we only have reason to attribute freedom to ourselves in situations in which we are aware that the moral law commands us categorically. We do not have a similar reason to believe we are free in purely prudential choices. Thus, the scope of transcendental freedom is not rational agency in general, but only moral agency.