Our age is the age of criticism, to which everything must be subjected. The sacredness of religion, and the authority of legislation, are by many regarded as grounds of exemption from the examination of this tribunal. But, if they on they are exempted, they become the subjects of just suspicion, and cannot lay claim to sincere respect, which reason accords only to that which has stood the test of a free and public examination.In the previous post I said that Kant was not concerned to rescue religion from the onslaught of science but to rescue science from the onslaught of empiricism. I confess that this is something of an exaggeration. A truer account might be to say that Kant was concerned to rescue metaphysics from the onslaught of metaphysics.
Kant wrote that the purpose of writing "Critique of Pure Reason" was to set metaphysics on a sounder basis and make it like a science. "Pure reason" here refers to abstract reasoning of the type that is done in mathematics, logic and theoretical physics. Pure reason is also called speculative reason, and is contrasted to practical reason which is reason applied to actual things and specific events as opposed to abstractions.
Kant was motivated by the work of David Hume who had argued against metaphysics in general and who said that all of metaphysics is meaningless. Kant said that David Hume had missed something important --that Hume's criticism applied as well to all sorts of pure reasoning including mathematics and theoretical science. Kant therefore had to rescue science from Hume before he could rescue metaphysics from Hume, which he had to do before he could rescue metaphysics from itself.
Now, this is not to say that Kant did not think his new method would help religion. He remarked in a few places that once his theory was accepted, people would stop making unjustified inferences about things that they could know nothing about and that religion would benefit from this, but I think he had in mind as much the attempts to prove that God exists as the attempts to prove that God does not exist. Furthermore, this is an occasional side theme, not the main drive of the book.
As to whether Kant was being an irrationalist, here is the paragraph containing the quote that Hicks takes out of conext (in fairness to Hicks, it is practically impossible to quote Kant in context because he relied so much on precisely-defined terms with definitions that are very hard to explain. You are about to read an example of this problem):
The positive value of the critical principles of pure reason in relation to the conception of God and of the simple nature of the soul, admits of a similar exemplification; but on this point I shall not dwell. I cannot even make the assumption- as the practical interests of morality require- of God, freedom, and immortality, if I do not deprive speculative reason of its pretensions to transcendent insight. For to arrive at these, it must make use of principles which,[I have highlighted the controversial quotation in bold type.]
in fact, extend only to the objects of possible experience, and which cannot be applied to objects beyond this sphere without converting them into phenomena, and thus rendering the practical extension of pure reason impossible. I must, therefore, abolish knowledge, to make room for belief. The dogmatism of metaphysics, that is, the presumption that it is possible to advance in metaphysics
without previous criticism, is the true source of the unbelief (always dogmatic) which militates against morality.
Kant is making a technical point here about knowledge that requires that you understand his theory of knowledge --a theory that he spent hundreds of pages of dense German run-on sentences to explain. I only have a few paragraphs to accomplish the same task, so if you read on I congratulate you for your fortitude.
Imagine that you are looking at a red ball sitting on a table. The ball might be made of rubber or stone and the two images would still be the same. Maybe it is not a ball at all, but just a half of a ball. Without moving, you can't tell what is on the other side. Apparently there is a distinction between the thing that you sense and the thing that is really there. Let's call the thing that you sense a "phenomenon" and what is really there the "noumenon" (the plurals of these words are "phenomena" and "noumena"). Notice that not only can one phenomenon apply to two different noumenon (that is, two different things might look the same), but also two different phenomenon can apply to one noumenon --that is, the same thing looks different from different perspectives.
So, apparently noumenon is a physical object and a phenomenon is just what it looks like. Let's look a bit more closely at this. What if you are wearing 3D glasses and looking at a computer-generated 3D image, what is the noumenon? There isn't really a ball there at all. If the ball rolls across the table, you aren't seeing the action of physical mechanical forces; you are seeing the complex effects of digital electronics. The noumenon is explained in terms of digital circuits or computer programs.
Now consider a third possibility: you are dreaming. In this case you can see the same phenomenon but now the noumenon is something in your brain activity. In the case of dreaming or 3D computer animation, the noumenon doesn't look anything like the phenomenon. Not only doesn't it look like it, they don't even have similar relationships. Just because one phenomenal ball is above another phenomenal ball, that does not mean that the noumenon associated with one is physically above the noumenon associated with the other. If you are dreaming, you have no idea how the related brain states are related to each other, or even if they are distinct brain states. That is, just because you see two different balls in a dream, that does not mean that there are really two distinct brain states that these balls are phenomena of.
If you think about it, we really have no idea, even in the normal world, what noumena are really like. We think we know what a volleyball is like --it is spherical, it weighs a certain amount, it behaves a certain way when you hit it-- but when you think about it, all of those things are phenomena. What is really there under the appearance, underneath the information that we get from our senses? Any time that you try to answer this question you come back to sense information. You just cannot explain what is there without talking about phenomena. You can't even say where the noumenon is, as shown by the computer and dream examples. In both of those examples, the noumenon was in a completely different place from the phenomenon. In fact, space itself is a phenomenon. Ultimately, you can't even know for sure that the noumena exist. You can't say for sure that there is any distinct underlying reality underlying what you perceive as a ball.
This is a real philosophical problem (meaning that it doesn't really matter to anyone except philosophers). How can we ever get past appearances, past phenomena to find out what the noumena are really like? Kant's answer is that we can never have true knowledge of noumena. Kant called access to the noumena "transcendent insight" in the quote above.
Kant is using the work "knowledge" to apply to what we know about phenomena rather than what we know about noumena. This might seem backwards: shouldn't knowledge be about the real thing instead of just about the appearance? But that is impossible; according to Kant, we have no transcendent insight. We can think about the real thing. We can form beliefs about it, but we can't have any knowledge because our knowledge about the world comes only from one source: sense data (there are other kinds of knowledge as well, but they do not apply to the world, only to concepts or abstractions such as in mathematics). Since all of our knowledge about the world comes from sense data and sense data is all phenomenal, it follows that all of our knowledge about the world is about the phenomena rather than about the noumena.
In the sentence just before the one about abolishing knowledge is this: "For to arrive at these, it must make use of principles which, in fact, extend only to the objects of possible experience, and which cannot be applied to objects beyond this sphere without converting them into phenomena, and thus rendering the practical
extension of pure reason impossible." In other words, "to arrive at these" (to assume the existence of God, morality and immortality or the soul) Kant cannot use principles that apply only to "objects of possible experience" (only phenomena are objects of possible experience) without first converting the noumena (God and soul) into phenomena which would render the practical extension of pure reason impossible.
I think what he means by that last bit is that although you can reason from the phenomena to talk about what something is like, the phenomena alone are not enough to tell you that something actually exists because existence is a property of the noumena. In effect, you can never have true knowledge that something exists, you can, at most, have belief. Now this applies to rocks and trees as well as it applies to God and the soul, but the difference is that for rocks and trees it doesn't really matter if the noumena exist. If a rock is nothing more than a phenomenon, it is still going to hurt your head if someone throws it, so you'd better duck. After all, your head is only a phenomenon too. It doesn't matter what the "real underlying truth" is because in the physical world all we have are phenomena and that is what really matters.
So this is what Kant is saying: We can never have true knowledge that God and the soul exist because (noumenal) existence is not something that we can have true knowledge about.
This is not an expression of irratinoalism. Quite the contrary, it is an attempt to use rational thought to carefuly demarcate what we know from what we merely believe.