Kant’s ideas are so counterintuitive that they produce an almost visceral resistance. The notion that reality might be completely different from how it presents itself to us seems absurd, unreal, and impossible to take seriously. We resist Kant emotionally, no matter how compelling his argument. Normally reasonable people like Dennett respond to Kant with evident impatience. They are unable to answer his argument, but they pretend that it is not necessary to answer it. This attitude may be termed the “fundamentalism” of reason. It is reason so sure of itself that it refuses to consider reasonable criticism. Reason has become irrational and now relies entirely on simple intuition or “common sense.”

Common sense, however, is not always a reliable guide to the truth. Common sense tells us that the earth is stationary and that the sun goes around it. Common sense tells us that an object is naturally at rest and that a moving object must automatically come to a stop. Common sense tells us that space and time are absolute. All these simple intuitions are false. In fact, the great discoveries of modern science—from Copernicus to Galileo to Newton to Einstein to Bohr to Heisenberg—are all massive violations of common sense. That is why in several cases the geniuses who first put forward those ideas were dismissed as crackpots. We now know that these crackpots were right. So it is a fact, not a matter of opinion, that reality is sometimes very strange and that common sense does not give us an unfailingly accurate picture of the world. To proclaim that it always does is to expose oneself as an ignoramus. Common sense, philosopher Bertrand Russell once said, is the”metaphysics of savages.”

Kant recognized that he was producing a revolution in human understanding. Just as Copernicus had turned the world “upside down” and forever altered the way we perceive the earth in relation to the sun, so Kant considered his own philosophy as producing a kind of Copernican revolution in thought. Of course people will still continue to perceive the world pretty much in realist terms—just as we go about our daily lives without worrying about the fact that we live on a planet hurtling through space at many thousands of miles per hour— but even so, this realism has been exposed as an illusion.

The illusion of realism is that it mistakes our experience of reality for reality itself. Realists like Dennett think of themselves as tough- minded empiricists, but they are not empirical enough to realize that all that is available to them are experiences and nothing beyond them. It is Kant, the transcendental idealist, who starts with experience and then proceeds from it by steps that reason can justify. By contrast, the empiricist begins with a presumption that is impossible to validate, and his whole philosophy is constructed on that dubious premise. The empiricist assumes without any evidence or proof that his experiences somehow give him a magical access to reality. So completely does he identify experience and reality that he cannot liberate himself from thinking of the two as one and the same. In equating experience and reality he is making a huge and unwarranted leap, but this breakdown of reason is not easy for him or us to recognize because our human minds have a built-in disposition toward illusion: the illusion that reality must be exactly the way we experience it. The irony is that many of the people who proceed in this irrational way think of themselves as following strictly along the pathways of reason. Their outlook can survive scrutiny only as long as they do not examine its foundations.

To their credit, there are a few “brights” who take Kant seriously and attempt to answer his arguments. Kant cannot be right in saying that we have no access to reality, they say, because you and I and everyone else experience the same reality. When we are in a room, we see the same lamps and tables and books on the shelf. Obviously those must exist and we must have direct access to them; otherwise we would not all have the same perception of them. But Kant’s answer is that because we are all human beings, we have the same sensory equipment, and it operates in each of us in the same way. Therefore we all have the same experience, but the experience is all we have. Just because we have similar or even identical experiences does not mean that any of us has access to a reality that is beyond that experience.