There is a deep disagreement between the constructivists and realists about the fundamentally right ways to interpret Kant’s moral philosophy. The problem of the source of value is one example that is at the very heart of the meta-ethical divide between these two views. Christine Korsgaard is a constructivist figure who argues that rational beings become the source of value by conferring value on the objects of their rational choice. Paul Guyer is a value realist who defends that freedom is the ultimate source of value that is not constructed but recognized by rational beings as really valuable in itself. Each side has its own textual strength from Kant’s ethical writings. In this paper, I argue that Guyer’s realist position can endorse Korsgaard’s notion of value-conferring rational choice in the case of particular (nonmoral) ends. I present their own accounts on the source of value. Then, I present and discuss transcendental and naturalistic accounts of freedom in Guyer’s interpretation of Kant. Contrary to Guyer, I opt for the former in the form of practical freedom and defend that it can still retain his substantive thesis that freedom is the value realized by adherence to the moral law. I make a distinction between the value of particular ends and the value of free agency. I defend a realist reading of the Formula of Universal Law on the basis of the Formula of Humanity, in which humanity is the negative end of the categorical imperative. I argue that this reading can show that rational choice confers value on its objects by recognizing the value of free agency. At the end, I present it as a novel realist approach, in which freedom is the condition and source of value for constructing particular values in our lives.