In philosophy of the mind, most of the debate during the past century has turned on the materialist and the dualist perspectives. Materialists have argued that physical things are really the only things that exist, and that the mind is a physical thing, and dualists have argued that the mind and body are immaterial and material things, respectively. Both materialism and dualism suffer from well-trod problems — materialism seems to explain away, rather than explain, the mind, and dualism notoriously suffers from the interaction problem — how does an immaterial mind interact with a material brain?

I believe that materialism has more problems than dualism, as you might have guessed, but neither is satisfactory and there are other ways to understand the mind.

Idealism is the view that everything is immaterial mind and physical things qua physical don’t actually exist. It has had venerable defenders, but is hard to take seriously. Famously, Dr. Samuel Johnson, when asked how he could refute Berkeley’s idealism, said “I refute it thus” and kicked a rock.

Another explanation for the mind is provided by Thomistic dualism, which presupposes Aristotelian and Thomist metaphysics and proposes that the mind bears the same relation to the body that form bears to matter. I believe that it is the most satisfactory explanation for the mind.

A fifth approach to understanding the mind is neutral monism, championed by Bertrand Russell. Russell was, as you probably know, an atheist, but not a materialist. His observations on philosophy of the mind are cogent, and of surprising relevance to our modern debate on scientism.

Russell began with affirmation of indirect realism. He posited that our sensory perceptions do not necessarily present us with the world as it is. We have no reason to think that red things have “redness” in them. Atoms have no intrinsic color. We perceive red because of the way our perceptive system processes light of a certain frequency. We perceive phenomena — things as they appear, not noumena — things as they are.

But Russell pointed out that the scientific investigation of the natural world — which would seem to present us with a much more secure picture of reality — has its own problem. It’s a serious problem. Russell pointed out that scientific knowledge of the physical world entails causal explanations of particles — electrons and protons and photons are described in terms of how they interact with other particles. Substances are described by science according to what they do. Science does not describe substances — electrons, protons, photons and aggregates composed of them — by what the are.

Russell holds to structural realism — the view that science tells about the causal relations (the causal structure) of real things, but does not tell us exactly what those things are, in themselves. For example, the brain is understood under scientific investigation as matter related by a complex simulacrum of causal events — atoms and molecules and action potentials. But science is silent — must be silent — on what the brain is in itself. Science describes relations we understand in nature, just as perceptions describe sensations we have of nature. Neither perceptions nor scientific understanding provide us with an understanding of nature as it actually is.

Is our quest for direct reliable knowledge of nature — nature as it really is — hopeless? Russell says no, and he makes a remarkable observation. Perception and scientific investigation do not exhaust our ways of knowing. We can also use introspection to know certain things. And unlike perception and scientific investigation of natural things like mental states, introspection is direct knowledge of mental states. It is the only kind of knowledge we have that is not mediated by sensory organs or conjured from scientific study of causal relations.

By introspection we know our mental states as they really are.

Russell argues that, in philosophy of the mind, the materialists have it exactly backwards. Materialists reduce the mind to the brain, trying to explain the mind in terms of appearances and causal relations of brain tissue. But the reality is that it is the mind that we directly experience — the brain is reducible to the mind, so to speak, not the mind to the brain.

By neutral monism, Russell means that there is one kind of substance and it is neutral, in the sense that it is neither wholly mental nor wholly physical. This one kind of substance — he called it qualia — can be introspected, and can be perceived, and can be understood via scientific investigation of causal relations. But only introspection lets us know this monist substance (our mind/brain) as it actually is. Perception and scientific study merely give us indirect knowledge of our mind/brain.

Russell observes that if you want to know what the brain is like intrinsically, in itself, neuroscience won’t help you. You can know what the brain is like intrinsically only by contemplating your own thoughts. In a very real sense, you know more about your brain than any neuroscientist knows about it, because you know your brain (mind/brain) first-hand, not in a perceptual or abstract scientific way.

Russell proposed that qualia are the ultimate substance of which everything is composed. Qualia are intrinsically neither mental nor physical. When organized into neural structures, qualia are mental. When organized into non-neural structures (rocks, chairs, etc.) qualia are physical.

Russellian identity theory — neutral monism — has obvious strengths. In my view, its greatest strength is that it flips materialists’ arguments. It is the mind, not the brain, that is known directly and with certainty, and materialist theories that try to reduce the mind to the brain or eliminate the mind altogether (eliminative materialism) are fundamental errors.

The obvious weakness of Russellian neutral monism is the implication of pan-psychism — the notion that there is or at least can be a little bit of “mind” in everything, including inanimate objects. That seems to me to be a bit too much to accept as is, despite the significant strengths of the viewpoint.

In addition to refuting materialism, as Russell’s theory nicely and decisively does, neutral monism makes scientism, which is the view that scientific investigation is the ultimate arbitrator of our understanding of nature, a difficult proposition to defend. The scientific endeavor, laudable and effective as it undoubtedly is in some circumstances, is sharply limited. Science can only investigate causal relations between things, not the things in themselves.

The only things we can know directly, in themselves, are our own mental states.

Introspection, not perception nor science, provides the only direct kind of knowledge.

(NB: Ed Feser’s Philosophy of Mind: A Beginner’s Guide is an excellent introduction to these philosophical conundrums. He provides a balanced discussion of the broad range of philosophical approaches to the mind-brain question.)

Image: Bust of Bertrand Russell, Red Lion Square, London/Wikipedia.