Kant disagrees with some tenets of Christianity and agrees with others. He rejects the Christian doctrines of origin sin and salvation. Yet he also believes that Christianity is superior to other monotheistic religions, primarily because it encourages the development of a truly ethical community and a commitment to internal moral principles. In short, Kant sees the seeds of his own moral religion in Christianity.
According to Kant, a comparison between Judaism and Christianity shows how revolutionary the Christian faith can be. In his view, Judaism is a public religion, which means that its core principles are more akin to public laws than to internal moral principles. In fact, all of Judaism's "commands are of the kind which even a political state can uphold and lay down as coercive laws, since they deal only with external actions" (6:126). Additionally, Kant says, Judaism has restricted its membership to an exclusive group of people, thereby thwarting any possibility of developing into a universal church whose laws would apply to all people.
For Kant, Christianity is best understood not as a continuation of Judaism, but as the beginning of something new. In lieu of public laws governing moral behavior, Christianity requires internal laws that govern what is morally right. Kant lauds Christianity's inclusiveness, passing off such horrors as the Crusades and the persecution of the Jews as anomalies, unfortunate but isolated departures from the core message of this dominant world religion.
Kant goes on to explain that all religious faiths involve something holy that people can comprehend at least partially. Kant says that in worthwhile religions, this holy quality is usually embodied in a moral ruler of the world, a deity who has the final word on all moral questions and concerns. Some faiths articulate the relationship between the moral ruler and humanity better than others. For Kant, true religions believe in a God who is as a morally holy lawgiver, a benevolent ruler, and a just judge and administrator of his laws.
Just as Kant understands Jesus as the ideal of perfect morality, he understands God as an ideal. We do not literally owe allegiance to a holy lawgiver or an actual judge. Rather, we should interpret God allegorically, and let God inspire us to become holy, to counteract our natural tendency toward immoral conduct, and to urgently reform our own behavior. Kant believes that the moral wisdom in Christianity can be gleaned only from an allegorical understanding of Christianity.
Kant sees Christianity as the historical expression of truth that lies dormant in the human heart, waiting to be unearthed through conscientious reflection. If we do not discover this truth, we are responsible, for we did not search our own hearts long enough to uncover it.
Kant claims that Christianity articulates the relationship between the individual believer and God better than any other religious tradition. However, he does not advocate Christian faith in God. For Kant, Christian faith involves three beliefs: a basic belief in the existence of God, a set of beliefs about what God is like and what he intends for humans, and a set of beliefs about humans' obligations to God.
Kant explains why this kind of faith is not helpful for moral improvement in this passage, in which he says the Christian idea that one can know God "[is really just the profession of an] ecclesiastical faith totally unintelligible to human beings, or, if they think that they understand it, the profession of an anthropomorphic creed, and not the least would thereby be accomplished for moral improvement" (6:142). Here Kant says that human beings cannot be sure that God has particular characteristics, or that God has certain intentions toward humanity. Suck knowledge is simply beyond human understanding. That is why such a profession of faith would be "totally unintelligible to human beings." People are fooling themselves if they think they really understand God. Professing to know what God is and what he wants does absolutely nothing for our own moral improvement, Kant points out in this passage.
These comments strongly suggest that moral religion does not require strong faith in a particular God. This is especially true if faith in God involves making claims about what he or she is like, and what he or she requires of human beings. We cannot know what God is like, and claiming to know does not improve our moral character. If Kant advocates faith at all, it is the faith that we can become better people.