Allison、Timmermann等人对康德伦理学中定言命令式的演绎进行了重构,但他们在两个关键环节——理性和第三者——上存在着问题:一是理性等同于理论理性的观点不符合《纯粹理性批判》中的文本依据;二是对第三者的论述不符合它的决定性判据。其实,理性是纯粹理性,包含理论理性与实践理性两种不同功能,第三者是不完善意志,即受感性欲望刺激的意志与纯粹意志的结合体;从而挖掘出不为人关注的自由的演绎,以及定言命令式演绎的三个要素:两重世界成员、知性世界的权威性和第三者;最后将演绎思路重构为七个步骤。 Allison, Timmermann and others reconstructed the imperative imperative deduction in Kant’s ethics. However, they have some problems in two key aspects: reason and third party: one is that rationality is equal to theoretical rationality The viewpoint does not accord with the textual basis in Critique of Pure Reason; the second is that the discussion about the third party does not accord with its decisive criterion. Actually, reason is pure rationality, which contains two different functions: theoretical rationality and practical rationality. The third one is the imperfect will, that is, the combination of the will stimulated by sensual desires and the pure will, so as to dig out the deduction of the freedom that nobody cares about , As well as the three elements of the imperative imperative deduction: the members of the double world, the authority of the intellectual world and the third party; and finally, the reconstruction of thinking is reconstructed into seven steps.