康德的道德神學，企圖把信仰建立在人類理性的基礎上。他一方面駁斥知性經驗與思辨理性對於掌握「靈魂不朽」與「上帝存在」命題的無能力，另一方面卻在實踐理性的基礎上確立這兩命題的必然性。因而強調：道德必然引至宗教。然而這又不可理解為道德法則自身必然直接產生宗教，而是以道德法則為線索，加上人性追求幸福本能的需求，也就是德福一致的最高善，才是宗教信仰的必然基礎。因此康德說宗教的必然性不是客觀的，而是道德上主觀的一種確信。從而這種宗教信仰的需要，即在於掃除道德障礙乃至激勵道德決心，而不可反過來將道德法則的客觀必然性建立在宗教信仰的基礎上。在這種理性信仰中，人所應關切的仍只是：是否成為有德而配享幸福，而不是如傳統基督教信仰那樣仰望奇蹟、神恩，乃至救贖與祈禱。

The ethical theology of Kant aims to vindicate the religious belief on the basis of human reason. Although he argues on the one hand that the knowledge of experience and the speculative reason are ineffective for making clear the statements of the immortality of soul and the existence of God, he, on the other hand, maintains on the basis of the practical reason the immortality of soul and the existence of God. Consequently, Kant stresses that morality is bound to lead to religion. However, the afore-mentioned argumentation of Kant is not be understood as that the moral principles themselves should directly lead to religion, from Kant’s point of view, the indispensable foundation for the religious belief has to be built with the framework of moral laws as well as the human instinctive desire for happiness, that is, the Highest Good of the proper proportioning of virtue and happiness is the true basis of the religious belief. Accordingly, Kant insists that the “moral necessity” to “assume the existence of God” is “subjective, i.e., a need, and not objective, i.e. duty itself.” Therefore, the necessity of the religious belief in Kantian viewpoint means to eliminate the moral obstacles so as to aspire the moral resolutions, not on the contrary, that the necessary objectivity of moral laws is established on the basis of religious belief. With such a rational religious belief, what the faithful should be concerned about is to introspect oneself whether one’s virtue is worthy of happiness, and not to behave in accordance with the traditional Christian ways to rely upon praying and look to divine grace, miracles as well as redemption.