Why do humans have consciousness? The arguments surrounding this question make it one of the most animated debates in contemporary philosophy.

One reason why consciousness so vexes academic philosophers is that a great many of them are atheists, and the reality of subjective consciousness frustrates an extremist but widely held version of atheistic metaphysics called eliminative materialism. This form of metaphysics takes the position that the only things that exist are matter and mindless physical processes. But in a world of pure matter, how could you have subjective, conscious beings like us?

To someone schooled in the great historical philosophical traditions — which have been largely dismissed following the adoption of post-modernism in the academy — this debate is immensely frustrating. In fact, much of the ongoing conversation about consciousness is self-evidently absurd.

"The scientific and philosophical consensus is that there is no nonphysical soul or ego, or at least no evidence for that," writes philosopher David Chalmers. The New York Times backed him up, calling this a "succinct" summation of the status quo. Except that it's not.

First of all, there can be no scientific consensus or evidence about nonphysical realities, because science is only concerned with physical realities. As for the "philosophical consensus," well, anyone who knows anything about philosophy knows that there has never been such a thing and never will be. And even if there were, it wouldn't mean anything, since philosophy is not a science; in science, an expert consensus does represent the state of the art of knowledge on a particular issue. In philosophy, it merely represents a fad.

So things are very open. But the debate is always presented as an alternative between two narrow and incomplete views: On the one hand, the materialist position that there is no such thing as consciousness; and on the other, Descartes' view that we have a kind of "ghost in the machine," a spiritual being living somehow "inside" of us, who gives us consciousness and mind. But, for example, to both Christian and ancient Greek philosophy (two of the most important streams of thought in philosophy), the "soul" is not a kind of ghost, but rather the form of the body, the uniting principle between mind and body.

Another argument on consciousness that enjoys a bit of consensus, especially lately, is that consciousness is an illusion. Our brain constructs models of the world around us and then tricks itself into believing that this is an expression of the world. The foremost proponent of this view is the philosopher Daniel Dennett.

But again, this view is literally nonsense. The concept of an illusion presupposes that there is a subjective consciousness experiencing the illusion.

Dennett's last book, From Bacteria to Bach and Back made this "illusion" argument by pointing out that our brains ceaselessly construct and modify and process the "raw data" from our senses into a coherent picture. The idea that our brains construct a not-completely-accurate picture of the world for us is not exactly new. Scientists have known this for decades, and philosophers for literally millennia. Any child can notice it: What we see when we open our eyes is a composite picture made by our mind using data from both of our eyes, which is why there are optical illusions and why if you block out one eye and then the other you will see things differently than with both eyes open. And, yes, this is true of everything else we experience, not just sight.

But this is a complete non-sequitur. That our conscious experience is constructed by our brain does not in any way shape or form prove that consciousness is an illusion. If I say that I'm going to see Shakespeare's Hamlet tonight, and you respond by saying, "That's not true, because Hamlet never existed," that fact would be irrelevant: I will still be sitting in a theater experiencing Shakespeare's Hamlet. The fact that our consciousness is in a large sense a "theater" is important to know, but it doesn't alter the fact that there is still "someone" watching the play.

In fact, this point could just as easily be taken as evidence for the existence of the spiritual world. Our brain ceaselessly constructs reality for us. Indeed, we only grasp reality through concepts, which are nonphysical realities. We only see a flower as red because we have a concept of the color red; there is no such thing as the color red in reality, only different wavelengths of light perceived by our nervous system and interpreted by our minds in such a way as to give us the utterly subjective experience of seeing something as red. In this sense, we have a much more intimate experience of the nonmaterial world of concepts, ideas, and the mind, than of the world of matter.

But the bottom line is this: Of course consciousness is not an illusion, since it's the only thing that we have direct, unmediated experience of. I am conscious of these lines, as you are of reading them. As Descartes pointed out, it's not just that consciousness is an illusion, it's that it's the only thing anybody can be certain of.

More and more, fewer and fewer people have read the books and learned about concepts that would have been regarded as utterly basic just a century ago. So continues the slow cultural forgetting of philosophical concepts and traditions that shape our lives. The world doesn't just run on power plants and computers, it also runs on ideas. Liberal democracy, social democratic marketplaces, human rights, all those things are ideas before they are put in motion, and while they can run on autopilot for a while, they start breaking down when people forget how they work.

People shouldn't say absurd things, especially when they are credentialed academics, and especially when those claims then seep into pop culture under the guise of "academic consensus." This isn't an argument for God; consciousness proves that matter is not the only thing in existence, but this does not necessarily prove there is a God. It's an argument for logic.