Kant states in the Critique of Pure Reason (English translation) that

Thus the entire armament of reason, in the undertaking that one can call pure philosophy, is in fact directed only at the three problems that have been mentioned. These themselves, however, have in turn their more remote aim, namely, what is to be done if the will is free, if there is a God, and if there is a future world. Now since these concern our conduct in relation to the highest end, the ultimate aim of nature which provides for us wisely in the disposition of reason is properly directed only to what is moral. (A801)

The Critique of Pure Reason translation used in the wikipedia article on the matter is

All the preparations of reason, therefore, in what may be called pure philosophy, are in reality directed to those three problems only [God, the soul, and freedom]. However, these three elements in themselves still hold independent, proportional, objective weight individually. Moreover, in a collective relational context; namely, to know what ought to be done: if the will is free, if there is a God, and if there is a future world. As this concerns our actions with reference to the highest aims of life, we see that the ultimate intention of nature in her wise provision was really, in the constitution of our reason, directed to moral interests only. (A801)

I happen to find the first translation clearer (it comes from the pdf I am reading), but Wikipedia derives its analysis from the second one.

Kant had before established that it is impossible to either prove or disprove the existence of God. Wikipedia interprets this passage as arguing that thus, the next step in determining whether to accept the existence of God is to see whether it is in our interest to believe in God.

Now, Kant had previously in his epistomological expositions established categories of reason, which we humans impose onto the world. He dealt with Hume's skepticism by arguing that when we humans observe the world, we impose the category of causality (under a relation of ideas in his table of judgement) onto the world, just like a person with red glasses imposed the color red onto the world (courtesy of Sophie's world).

In both instances, Kant defends the attacks on the belief of God and of casuality, showing that both cannot be rationally proven. But then, he defends bothc casuality and the belief in God through two different mechanisms; for casuality he places it as a category of understanding, while with God he argues that it is in the interest of man to believe in God.

Now, my question is whether these mechanisms are related? Is the defense of the belief of god related to the concept of categories of understanding, or are these two completely different ideas within Kant's philosophical framework? If they are related, how? (Any relevant passages from an internet source or Kant's Critique of Pure Reason would be appreciated.)

  • I have provided two translations, one from the text I am reading and the other the one the Wikipedia article on Kant uses.
    – Cicero
    May 26, 2015 at 0:19
  • The first translation is more precise. I checked the German text.
    – Jo Wehler
    Jul 2, 2015 at 16:30

1 Answer 1


I think this is a solid question, and one that might be difficult to fit into the format of an SE answer. Thus, I'll try to provide a brief sketch of what I take the longer answer to be.

First, I want to suggest that one needs to be very careful in how one uses "rational"/"reason" and "understanding"/"knowing" when speaking about Kant. In the paragraph where you write about "In both instances", you state "showing that both cannot be rationally proven", but I think this is slightly infelicitious. Kant thinks both causality and the existence of God cannot be known -- but not because they are not related to reason. Instead, it is that understanding / i.e. knowing / is the application of the categories to a thing that has been placed under the manifold of sensibility.

Thus, it makes no sense for causality to be knowable, because causality is one of the conditions of knowledge. (as in the Sophie's World account of red glasses).

Similarly, God does not fit under these categories either for Kant. Kant rejects the possibility of knowing God in this way through one of his antinomies.

With that distinction in hand, we can turn to the quotation you provide, note the last phrase "directed to moral interests only". It has been argued by several thinkers that the Critique of Pure Reason is a propaedeutic to Kant's moral philosophy, and this is one of the passages that supports that interpretation.

Thus, to see how God and causality differ, we might turn to Kant's moral philosophy, which on a very crude sketch makes causality in the world the antithesis of rational autonomy. This rational autonomy in turn depends on the existence of God. First, God serves as a final judge meting out proportional happiness to the goodness of agents at the end of time (this is called the proportionality thesis). In the Critique of Practical Reason, Kant calls "God a postulate of practical reason" (See 5:122-134). Also see Religion from around page 96.

To put it another way, God and causality belong to two distinct realms that the Kantian moral self finds itself in. In the one realm, the self's actions are determined (causally) by what has preceded the self. In the other realm, the self uses freedom (rational freedom) to determine the course of its actions in a way that is imperceptible when that self is viewed as an object (rendered through the categories of others or even the self) but which is intimately tied to the existence of God.

  • Thanks for the insightful answer. So while Kant argues that God, free will and the soul are unknowable, they are necessary postulates of practical reason. These postulates of practical reason are different from the categories of understanding that Kant writes about in the critique of pure reason (I haven't read the critique of practical reason, but have added it to my reading list!). Furthermore, there are two distinct realms that Kant's moral self finds him in; one where actions are determined causally, and another where the self uses rational freedom to determine the course of its actions.
    – Cicero
    May 26, 2015 at 0:33
  • Is my preceding comment essentially on the mark. Also, does Kant in his critique of practical reason discuss when the first realm where actions are causally determined applies, and when the second realm where the seld uses rational freedom (tied to God) to determine the course of events.
    – Cicero
    May 26, 2015 at 0:35
  • Kant thinks causal determination applies whenever we let anything other than our use of reason determine our actions. For an extended treatment of that issue, see Marcia Baron Kantian Ethics almost without Apology. (Depending on your purposes for reading I would put the Groundwork (sections 1 and 2) and Metaphysics of Morals (preface and then doctrine of virtue) ahead of Critique of Practical Reason)
    – virmaior
    May 26, 2015 at 1:18
  • Your first comment is basically right.
    – virmaior
    May 26, 2015 at 1:18
  • 1
    @Cheersandhth.-Alf I'm not really sure why you're trolling me but if you have a complaint, take it to meta. For the reference of anyone interested, here's the comment I deleted: "I wonder why one would try to understand what Kant thought about the Christian faith's god and causality. The former is unobservable, just a superstition, while the latter is very much observable in everything, and unless the impenetrable phrasing of this answer hides its implications, it seems that Kant failed to understand that trivial distinction."
    – virmaior
    May 26, 2015 at 12:39

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