The Mind/Body Problem, part I

Back to basics. Last year, we took a look at the introduction to John Heil’s excellent Philosophy of Mind (3rd ed, Routledge 2013) in “A Tree Falls” https://better-questions-than-answers.blog/2017/08/31/a-tree-falls/   He called it “The Unavoidability of the Philosophy Mind”, and here at BQTA we do indeed think that philosophy of mind is inevitable and unavoidable. You can try to ignore it, but that only leads to confusion, frustration and heartbreak, as we see in the news everyday.

As further valuable orientation, let’s look at Heil’s chapter “The Mind/Body Problem” in A Companion to Metaphysics (2nd ed 2009) edited by Jaegwon Kim, Ernest Sosa, and Gary Rosenkrantz. He takes an historical approach, roughly chronological. The goal is not to know the history itself–who said what when. The point is that the famous philosophers mapped out the main ideas on the mind-body problem, and it is those ideas that we’re interested in and still want to think about. 

So here it is, heavily edited, abridged, altered, and supplemented for our purposes. I hope the professor won’t mind.

The mind is “the great garbage bin ”. What seems real but lacks physical respectability we consign to the mind. A tradition started during the scientific revolution in the 17th century places “secondary qualities” (colors, tastes, sounds, odors) in the mind. These are thought not to be “out there”, but to be “subjective” transitory occurrences in the minds of observers. David Hume (1711-1776) regarded causation as a psychological “projection”, and it seems natural to distinguish the world as experienced from the world as it really is, that is, as revealed by science. The idea that minds incorporate non-worldly, non-physical elements, however, evidently places minds outside the physical realm. What science casts asunder, philosophers must piece together. Hence the mind–body problem.

Although he did not invent the mind–body problem, Descartes (1596 –1650) is responsible for its modern formulation. Immediately after proving his existence by noting that the thought expressed by “I exist” must be true if I can so much as consider whether it is true (Meditation 2), Descartes asks, “What am I?” He answers, “a thing that thinks”, a thinking substance. He thinks that he could doubt the existence of his body and the room he appears to be in; it might all  be a dream. But his mind must exist. Bodies are optional. Descartes regards planets and trees, not as substances, but as modes, ways extended matter is organized. On the one hand, we have extended substance and its modes: material bodies. On the other hand, we have thinking substances, minds, and their modes: thoughts, images, and feeling. Just as minds and bodies are irreconcilable (bodies are extended in space, minds are non-spatial), so modes of thought and modes of extension are incommensurable. Now we are faced with a problem: how could mental goings-on have material effects;  and how could material occurrences affect the mind? This is Descartes’s mind–body problem.

In fact there are two problems here. The first arises from the difficulty of understanding how spatial and non-spatial entities could engage causally. The difficulty is especially pressing for Descartes who regards mental and physical substances as operating on very different laws or principles.

A second difficulty arises from our conception of the physical world as a self-contained closed system. Physical events have, we suppose, purely physical causes—the causal closure of the physical. If non-physical minds affect the physical world, it looks as though they would have to initiate or intervene in physical processes. Were that so, the physical world would not be a closed system governed by physical law – a daunting prospect that seems to threaten the scientific enterprise.

The self-contained nature of the physical world could be expressed in terms of a conservation principle. Descartes, writing before Newton, imagined that what was conserved was motion. Minds could not initiate or inhibit motion in the physical world. Minds could, however, have physical effects without violating physical closure by altering the direction taken by material particles. This solution unraveled with Newton’s introduction of force, which moved physics from Cartesian kinematics to a dynamical system. Nowadays we think that what is conserved is mass–energy. In either case Descartes’s account of mind–body interaction is no longer viable.

Both Malebranche (1638 –1715) and Leibniz (1646 –1716) skirt the mind–body problem by rejecting mental–physical interaction altogether. If there is no mind–body interaction, there is no mind–body problem. Such maneuvers, however, exact a heavy price. Can we reasonably abandon the idea that physical events are causally connected? Could we ever be satisfied with an account of the world according to which mental occurrences – perceptual experiences, for instance – are not brought about by physical occurrences, and thoughts and decisions never give rise to actions and utterances? Must we settle for the idea that mind–body interaction is illusory?

Common sense says that mental goings-on cause physical events all the time. The pain in your knee caused you to skip your run. The sound of the siren caused you to pull the car over. And not just in humans: the taste of the treat is what gets your dog to pay attention. There are bio-chemical events too, of course, but can we believe that the taste itself has nothing to do with your dog’s excitement? Maybe that means that mental events just are nothing but—identical to— brain events. Or that the words we use that seem to refer to immaterial mental events, such as “pain” “sound” “taste”, are really just words for behavior. Both ideas were tried in the 20th century, but both were found unworkable.

For Descartes, mental and physical substances are, God aside, mutually exclusive and exhaustive. Each kind of substance has a distinctive attribute: mental substances think, but are not extended; physical substances are extended, but do not think. Mental and physical properties are modes of these attributes, determinate ways be being extended or thinking. Being spherical and being red are ways of being extended. An experience of a spherical red object, in contrast is a mode of thought, a way of being conscious.

Many of Descartes’s contemporaries and most of his successors rejected this picture. A mental substance might be a substance with mental properties; a physical substance, one with physical properties. This leaves open another possibility: some substances might have both mental and physical properties, a dualism of properties, not substances. Perhaps mental properties are just distinctive properties of certain complex physical systems. Can that solve the problem of mental causation?

Property dualism can be developed in various ways. According to Epiphenomenalists – T. H. Huxley (1825–1895), for instance – mental occurrences are by-products of brain processes. They resemble squeaks made by a complex machine that play no role in the machine’s operation. When you bark your shin, you feel a pain. This feeling is a result of a chain of events in your nervous system leading from your shin to a region of your brain. In the simplest case, the neurological event that “gives rise to” your painful sensation also produces bodily motions that might otherwise be thought to be caused by the sensation. Conscious states and bodily motions are correlated, not because consciousness is causally efficacious, but because conscious states and bodily motions have common causes.

On the one hand, epiphenomenalism enables us to sidestep worries about mental goings-on intervening in the physical world thereby violating closure. On the other hand, we are left with two significant worries. First, as in the case of Malebranche and Leibniz, we will need to abandon the idea that mentality makes a difference in what we do. You might worry about this, not merely because it seems on the face of it implausible, but because it is hard to see how consciousness could possibly bestow any sort of evolutionary advantage on creatures possessing it. True, consciousness could be an incidental by-product of evolutionarily adaptive physical processes. Stephen Jay Gould (1944-2002) called these “spandrels”: features which tag along in evolution but what are not themselves adaptive. It is hard to believe that consciousness itself is evolutionarily irrelevant, that it could be a mere spandrel. Consciousness seems like such a big deal.

A second worry concerns the production of conscious experiences. These are caused by physical processes in the brain, but how is this supposed to work? What exactly is involved in the production of a non-physical event?

Epiphenomenalists tell us that consciousness “arises from” the brain, but what is this “arising from” relation? Mental events presumably involve mental properties, but where are these properties? They seem not to be among those we discover when we probe the brain. Are they invisible? Are they somehow “outside” space or space–time? The Cartesian problem concerned how extended and non-extended things could interact. The problem arises anew for epiphenomenalism in relation to the production of mental properties or events. The situation appears bleak. We have a robust conviction that, although mental and physical properties are utterly different, interaction between minds and bodies is commonplace. The difficulty is to square this with closure, our conviction that the physical world as a whole is causally closed, mass–energy is conserved.

One elegant solution is to deny the existence of minds and mental properties altogether. If there are no minds, no mental properties, there is no mind–body problem. Thomas Hobbes (1588 –1679) argued that we are nothing more than elaborate machines. In a way, Hobbes is just extending Descartes’s official view. Descartes held that most human behavior and all behavior of non-human creatures could be explained mechanically. Only in the case of behavior resulting from rational mental processes (most notably linguistic behavior), do we need to posit mental causes. If ratiocination, however, were just a matter of calculation (think of a computing machine to get a feel for what Hobbes has in mind) we would have no need to imagine that our bodies are controlled by minds with distinctive mental properties.

A conception of this kind, materialism, can be developed in various ways. First, you might think, as Hobbes does, that mental states and properties are “reducible to”, that is identifiable with, physical states and processes. On this view, minds turn out to be nothing but brains, mental states and properties turn out to be nothing but physical states and properties. This is the mind-brain identity theory put forth in the 1950s by Australians U. T. Place and J. J. C. Smart. This eliminates the mental as a distinct realm. Another version of materialism might simply deny that there are minds or mental states or properties (Paul Churchland,“Eliminative Materialism and the Propositional Attitudes” 1981; Stephen Stich, Deconstructing the Mind 1996).

To see the difference, consider the discovery of DNA and its consequences for genetics. We now think we can map genes onto complex molecular structures, thereby “reducing” genes to DNA. However, genes remain respectable scientific entities. Compare reduction of this kind to the demise of phlogiston. Seventeenth-century chemists explained combustion by supposing that flammable materials contained phlogiston, a fluid driven out when the materials were heated. Advances in chemistry rendered phlogiston superfluous. Phlogiston was not reduced to more fundamental goings-on, but stricken from the scientific inventory. Eliminativists believe a similar fate lies in store for the mind. Perhaps the identity theorists would allow mental talk as a higher order description of brain activity.

According to eliminativists, talk of mental states and properties belongs to an outmoded “folk theory” of human and animal behavior. At one time we explained natural occurrences by supposing objects were animated by spirits. Such explanations were gradually supplanted by explanations adverting exclusively to physical processes. Those animistic spirits were eliminated. Nevertheless, we persist in regarding human bodies (and the bodies of most animals) as animated by spirits. We comprehend the behavior of intelligent creatures by supposing they are conscious of their surroundings and do what they believe will subserve their interests. Advances in neuroscience, however, promise to undermine “folk psychology” just as chemical discoveries undermined phlogiston.

You might worry that this way of framing the issues stacks the deck. Consider ordinary beliefs about ordinary objects: tables, trees, volcanoes. Physics and chemistry assure us that these things are at bottom just clouds of particles (or waves or something). We can explain the behavior of these particles without positing the ordinary entities, and there is no prospect of smoothly reducing the ordinary things to respectable physical– chemical kinds. Should we eliminate tables, trees, volcanoes? Mightn’t it be better to see talk of tables, trees, and volcanoes as reflecting an inventory of genuine objects that happen to be of no interest to the physicist or chemist? Physics and chemistry provide us with the deep story about the world, a world that includes the fundamental things and includes as well tables, trees, and volcanoes. These are not add-ons any more that the forest is something in addition to the trees.

Whether or not you are moved by such considerations, even tough-minded philosophers have found eliminativism hard to swallow. We can explain away – “eliminate”, consign to the garbage bin – ghosts by supposing that they are illusions, but it is hard to see how this could work with states of consciousness. Illusions seem ineluctably mental. An illusory feeling of pain is still a feeling. Conceiving of mental phenomena as “only in the mind” is scarcely a recipe for their elimination. The problem of reconciling illusions with the physical world is just the mind–body problem all over again.

Next: idealism, behaviorism and more on identity theory.

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