The following is adapted from my new book What's So Great About Christianity. For more information about the book, see my website dineshdsouza.com.

Bestselling atheist tracts like Richard Dawkins' The God Delusion, Daniel Dennett's Breaking the Spell, and Christopher Hitchens' God Is Not Great portray religion as an unreasonable form of "blind faith," often leading to fanaticism and even violence. Some of these atheists call themselves "brights," implying that they are the smart people who base their opinions on reason and science and don't fall for silly superstitions. But for all their credentials and learning, the atheists have been duped by a fallacy. This may be called the Fallacy of the Enlightenment, and it was first pointed out by that great Enlightenment philosopher, Immanuel Kant.

The Fallacy of the Enlightenment is the glib assumption that human beings can continually find out more and more until eventually there is nothing more to discover. The Enlightenment Fallacy holds that human reason and science can, in principle, unmask the whole of reality. In his Critique of Pure Reason, Kant showed that this premise is false. In fact, he argued, that human knowledge is constrained not merely by how much reality is out there but also by the limited sensory apparatus of perception we bring to that reality.

Consider a tape recorder. Being the kind of instrument it is, a tape recorder can capture only one mode of reality: sound. Tape recorders can "hear" but they cannot see or touch or smell. Thus all aspects of reality that cannot be captured in sound are beyond the reach of a tape recorder. The same, Kant says, is true of human beings. The only way we apprehend reality is through our five senses. But why should we believe, Kant asked, that our five-mode instrument for apprehending reality is sufficient for capturing all of reality? What makes us think that there is no reality lies beyond our perception, reality that simply cannot be apprehended by our five senses?

Moreover, the reality we apprehend is merely our experience or "take" on reality. How can you know that your experience of things is in any way like the things-in-themselves? Normally you answer this question by considering the two things separately and then comparing them. I can tell if my daughter's drawing of her teacher looks like the teacher by placing the portrait and alongside the person. I compare the copy or portrait with the original.

Kant points out, however, that we can never compare our experience of reality to reality itself. All we have is the experience, and that's all we can ever have. We have only the copies, but we never have the originals. So we have no basis for presuming that the two are even comparable. When we equate experience and reality, we are making an unjustified leap.

It is essential to recognize that Kant isn't diminishing the importance of experience or what he called the phenomenal world. That world is very important, because it is the only one our senses and reason have access to. It is entirely rational for us to believe in this phenomenal world and to use science and reason to discover its operating principles. But Kant contended that science and reason apply to the world of phenomena, of things as they are experienced by us. Science and reason cannot penetrate what Kant termed the noumena: things as they are in themselves.

Some critics have understood Kant to be denying the existence of external reality or of arguing that all of reality is "in the mind." Kant emphatically rejects this. He insists that the noumenon obviously exists because it is what gives rise to phenomena. In other words, our experience is an experience of something. Perhaps the best way to understand this is to see Kant as positing two kinds of reality: the reality that we experience and reality itself. The important thing is not to establish which is more real, but to recognize that human reason operates only in the phenomenal domain of experience. We can know of the existence of the noumenal realm, but at this point reason has reached its limit.

In Kant's view, the limits of human reason cannot be erased by the passage of time or by further investigation and experimentation. Rather, they are intrinsic to the kind of beings that humans are, and to the kind of apparatus that we possess for perceiving reality. The implication of Kant's argument is that reality as a whole is, in principle, inaccessible to human beings. Put another way, there is a great deal that human beings simply will never know.

So powerful is Kant's argument here that his critics have been able to answer him only with derision. When I challenged Daniel Dennett to debunk Kant's argument, he posted an angry response on his website in which he said several people had already refuted Kant. But he didn't provide any refutations, and he didn't name any names. Basically Dennett was relying on the argumentum ad ignorantium-the argument that relies on the ignorance of the audience. In fact, there are no such refutations.

Although Kant's argument seems counterintuitive-in the way that some of the greatest ideas from Copernicus to Einstein are counterintuitive-no one who understands the central doctrines of the world's leading religions should have any difficulty grasping his main point. Kant's philosophical vision is entirely congruent with the teachings of Hinduism, Buddhism, Islam, Judaism and Christianity.

It is a shared doctrine of those religions that the empirical world we humans inhabit is not the only world there is. Ours is a world of appearances only in which we see things in a limited and distorted way, "through a glass darkly," as the apostle Paul writes in his first letter to the Corinthians 13:12. Ours is a transient world that is dependent on a higher, timeless reality. That reality is of a completely different order from anything we know, it constitutes the only permanent reality there is, and it sustains our world and presents it to our senses. Christianity teaches that while reason can point to the existence of this higher domain, this is where reason stops: it cannot on its own investigate or comprehend that domain.

Thus when Christopher Hitchens and other atheists routinely dismiss religious claims on the grounds that "what can be asserted without evidence can also be dismissed without evidence," they are making what philosophers like to call a category mistake. We learn from Kant that within the domain of experience, human reason is sovereign, but it is in no way unreasonable to believe things on faith that simply cannot be adjudicated by reason.

When atheists summarily dismiss the immortality of the soul or the afterlife on the grounds that they have never found any empirical proofs for either, they are asking for experiential evidence in a domain which is entirely beyond the reach of experience. In this domain, Kant argues, the absence of evidence cannot be used as the evidence for absence.

Notice that Kant's argument is entirely secular: It does not employ any religious vocabulary, nor does it rely on any kind of faith. But in showing the limits of reason, Kant's philosophy "opens the door to faith," as the philosopher himself noted.

So the new atheists and self-styled "brights" can do their strutting, but Kant has exposed their ignorant boast that atheism operates on a higher intellectual plane than theism. Rather, as Kant showed, reason must know its limits in order to be truly reasonable. The atheist foolishly presumes that reason is in principle capable of figuring out all that there is, while the theist at least knows that there is a reality greater than, and beyond, that which our senses and our minds can ever apprehend.