Why Does the World Exist: An Existentia - By Jim Holt Page 0,89

conscious states over and above those of its individuals? Could it experience, say, the taste of peppermint?

The conclusion the philosophers who come up with these thought experiments want us to draw is that there is more to consciousness than the mere processing of information. If this is true, then science, insofar as it describes the world as a play of information states, would seem to leave out a part of reality: the subjective, irreducibly qualitative part.

One could, of course, simply deny that reality has such a subjective part. And there are philosophers who do deny it—Daniel Dennett, for one. Dennett refuses to concede that consciousness contains any intrinsically qualitative elements. As far as he is concerned, “qualia” are a philosophical myth. If something cannot be described in purely quantitative and relational terms, it is simply not a part of reality. “Postulating special inner qualities that are not only private and intrinsically valuable, but also unconfirmable and uninvestigatable is just obscurantism,” he declares.

Such denialism leaves philosophers like Searle and Nagel incredulous. It seems willfully blind to the very essence of what it means to be conscious. Nagel has written, “The world just isn’t the world as it appears to one highly abstracted point of view”—that is, to the scientific point of view.

The inner nature of consciousness yields one reason for thinking that there is more to the world than pure structure. But apart from the issue of consciousness, there are more general grounds for suspecting that cosmic structuralism is inadequate as a picture of reality. Structure by itself just doesn’t seem enough for genuine being. As the British idealist philosopher T. L. S. Sprigge put it, “What has structure must have something more to it than structure.” Perhaps Aristotle was right: you need stuff too. Stuff is what gives existence to structure, what realizes it.

But if that is true, how can we come to have knowledge of the ultimate stuff of reality? Science, as we have seen, reveals only how the stuff is structured. It does not tell us how the quantitative differences it describes are grounded in differences in any underlying qualitative stuff. Our scientific knowledge of reality is thus, in Sprigge’s words, “rather like the kind of knowledge of a piece of music which someone born deaf might have from a musical education based entirely on the study of musical scores.”

Yet there is one part of reality that we do know without the mediation of science: our own consciousness. We experience the intrinsic qualities of our conscious states directly, from the inside. We have what philosophers call “privileged access” to them. There is nothing whose existence we are more certain of.

Now, this raises an interesting possibility. Maybe the part of reality we know indirectly through science, the physical part, has the same inner nature as the part we know directly through introspection, the conscious part. In other words, maybe all of reality—subjective and objective—is made out of the same basic stuff. That is a pleasingly simple hypothesis. But isn’t it a bit crazy? Well, it didn’t strike Bertrand Russell that way. In fact, it was essentially the conclusion Russell reached in The Analysis of Matter. Nor did it strike the great physicist Sir Arthur Eddington as crazy. In The Nature of the Physical World (1928), Eddington ringingly declared that “the stuff of the world is mind-stuff.” (The term “mind-stuff,” by the way, was coined by William James in the first volume of his 1890 work, Principles of Psychology.)

Crazy or not, the idea that the fundamental stuff of reality is mind-stuff has one very odd implication. If it is true, then consciousness must pervade all of physical nature. Subjective experience would not be confined to the brains of beings like us; it would be present in every bit of matter: in big things like galaxies and black holes, in little things like quarks and neutrinos, and in medium-sized things like flowers and rocks.

The doctrine that consciousness pervades reality is called “panpsychism.” It seems to harken back to primitive superstitions like animism—the belief that trees and brooks harbor spirits. Yet it has attracted quite a bit of interest among contemporary philosophers. A few decades ago, Thomas Nagel showed that panpsychism, for all its apparent daftness, is an inescapable consequence of some quite reasonable premises. Our brains consist of material particles. These particles, in certain arrangements, produce subjective thoughts and feelings. Physical properties alone cannot account for subjectivity. (How could the ineffable experience of tasting a strawberry ever arise from the equations