Can we know that we are free in this transcendental sense? Kant’s response is tricky. On the one hand, he distinguishes between theoretical knowledge and morally justified belief (A820–831/B848–859).  We do not have theoretical knowledge that we are free or about anything beyond the limits of possible experience, but we are morally justified in believing that we are free in this sense. On the other hand, Kant also uses stronger language than this when discussing freedom. For example, he says that “among all the ideas of speculative reason freedom is the only one the possibility of which we know a priori, though without having any insight into it, because it is the condition of the moral law, which we do know.” In a footnote to this passage, Kant explains that we know freedom a priori because “were there no freedom, the moral law would not be encountered at all in ourselves,” and on Kant’s view everyone does encounter the moral law a priori (5:4). For this reason, Kant claims that the moral law “proves” the objective, “though only practical, undoubted reality” of freedom (5:48–49). So Kant wants to say that we do have knowledge of the reality of freedom, but that this is practical knowledge of a practical reality, or cognition “only for practical purposes,” by which he means to distinguish it from theoretical knowledge based on experience or reflection on the conditions of experience (5:133). Our practical knowledge of freedom is based instead on the moral law. The difference between Kant’s stronger and weaker language seems mainly to be that his stronger language emphasizes that our belief or practical knowledge about freedom is unshakeable and that it in turn provides support for other morally grounded beliefs in God and the immortality of the soul. 