TOWARD A NATURALISTIC ACCOUNT OF MIND

LEE SMOLIN

Theoretical physicist, the Perimeter Institute; author, Time Reborn

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“To think” can mean to reason logically, which certainly some machines do, albeit by following algorithms we program into them. Or it can mean “to have a mind,” by which we mean that a machine experiences itself as a subject, endowed with consciousness, qualia, experiences, intentions, beliefs, emotions, memories. When we ask whether a machine can think, we’re really asking whether there can be a completely naturalistic account of what a mind is. I’m a naturalist, so I believe the answer must be yes.

Certainly we’re not there yet. Whatever the brain is doing to generate a mind, I doubt that it’s only running prespecified algorithms, or doing anything like what present-day computers do. We likely have yet to discover key principles by which a human brain works. I suspect that how and why we think cannot be understood apart from our being alive, so before we understand what a mind is, we’ll have to understand more deeply what a living thing is—in physical terms. The construction of an artificial mind probably has to wait until we do.

This understanding will have to address what David Chalmers calls “the hard problem of consciousness”: how to account for the presence of qualia in the physical world. We have reason to believe that our sensations of, say, the color red are associated with certain physical processes in our brains, but we’re stumped because it seems impossible to explain in physical terms why or how those processes give rise to qualia.

A key step toward solving this hard problem is to situate our description of physics in a relational language. As set out by Leibniz, the patron saint of relationalism, the properties of elementary particles have to do with relationships with other particles. This has been a very successful idea, well realized by general relativity and quantum theory, so let’s adopt it.

The second step is to recognize that events or particles may have properties that aren’t relational—not described by giving a complete history of the relationships they enjoy. Let’s call these internal properties.

If an event, or a process, has internal properties, you cannot learn about them by interacting with it or measuring it. If there are internal properties, they aren’t describable in terms of position, motion, charges, or forces—i.e., in the vocabulary physicists use to talk of relational properties. You might, however, know about a process’s internal properties by being that process.

So let’s hypothesize that qualia are internal properties of some brain processes. When observed from the outside, those brain processes can be described in terms of motions, potentials, masses, charges. But they have additional internal properties, which sometimes include qualia.

Qualia must be extreme cases of being purely internal. More complex aspects of mind may turn out to be combinations of relational and internal properties. We know that thoughts and intentions can influence the future.

There’s much hard scientific work to do to develop such a naturalistic account of mind—one that’s nondualist and not deflationary, in that it doesn’t reduce mental properties to the standard physical properties or vice versa. We may want to avoid naïve panpsychism, according to which rocks and wind have qualia. At the same time, we want to remember that if we don’t know what it’s like to be a bat, we also don’t know, really, what a rock is, in the sense that we may know only a subset of its properties—those that are relational.

One troubling aspect of mind from a naturalistic perspective is our impression that we sometimes think novel thoughts and have novel experiences, which have never been thought or experienced before in the history of the world. Little would make sense about the human world of culture and imagination without allowance for the genuinely novel. A century ago, the Edge website didn’t exist and likely couldn’t have been imagined. Yet it exists, and as naturalists we must have a conception of nature that includes it. This must allow novel kinds of things to come to exist in nature.

We’re hamstrung by the conviction that nothing truly new can happen in nature because everything is really elementary particles moving in space according to unchanging laws. Without deviating an inch from rigorous naturalism, however, we can begin to imagine how our understanding of nature can be deepened to allow for the truly novel to occur.

First, in quantum physics we admit the possibility of novel properties arising that are shared among several particles in entangled states. In the lab, we can make entangled states of complex systems that are unlikely to have natural precedents. Hence we can, and do, create physical systems with novel properties. (So, by the way, does nature, when natural selection produces novel proteins that catalyze novel reactions.)

Second, Leibniz’s principle of the identity of the indiscernible implies that there can be no two distinct events with exactly the same properties. This means that the fundamental events cannot be subject to laws that are both deterministic and simple, for if two events have precisely the same past, their futures must differ. This presumes a physics that can distinguish the future from the past.

Note that quantum physics is inherently nondeterministic.

Does this imply that quantum physics will play a role in a future naturalistic account of mind? It’s too soon to tell, and the first efforts in this direction are unconvincing. But what we learn is that a naturalistic account of mind will require deepening our concept of the natural. We can think novel thoughts by which we can alter the future. Novelty must then be intrinsic to how we understand nature, if minds are to be natural. Therefore, to understand how a machine could have a mind, we must deepen our concept of nature.