Chapter 1: The Problem

The Mind/Body Problem

One formulation of the mind/body problem is the following incompatible tetrad:

1 - Bodies are physical.1

2 - Minds are not physical.

3 - Minds and bodies interact.

4 - The physical and non-physical can't interact.

Although any three of these propositions are compatible with each other, the four together are not. Thus, as formulated here, any solution to the mind/body problem must deny one or more of these propositions, and it must give a good reason for doing so. In order to determine which proposition(s) we can discard, it is best to define the terms in the tetrad.

Before I commence with the definitions, I must say a word about the process I will use in coming up with each definition. It is not enough for me to define each term in terms of any characteristics that distinguish it from my other terms. I intend to define each term by identifying its fundamental characteristic. The fundamental characteristic of something as something is that which makes it that something. The fundamental characteristic of a genus is that which makes possible most or all of the other characteristics that distinguish one genus from another.

As an example, anthropologists are often wondering what it is that distinguishes homo sapiens from the other animals. Many characteristics suggest themselves. Humans possess many abilities that separate them from the animals. They can write computer programs, fall in love, read, compose music, and design rockets. Certain bodily characteristics also distinguish humans from animals. For the most part, the opposable thumb, the large bridged nose, and the shape of the human foot all set humans apart from the animals. Nevertheless, none of these abilities, and none of these bodily characteristics, is the fundamental characteristic of humanity.

The characteristic that makes possible most of the characteristics that set humans apart from animals is reason. Given that all humans are animals, the fundamental characteristic of humanity is rational animality. It is reason that makes it possible for us to read, to write computer programs, and even to fall in love. (Branden, p. 37) Although we could recognize humans by these characteristics without worrying about what the fundamental characteristic of humanity is, it would be unphilosophical to do so. In the same vein, it would be unphilosophical to define the following terms by any common characteristic but the fundamental one.

Definitions of Terms

The Body

The body is that which we perceive ourselves to be with our senses. It usually includes arms, legs, a head, and so on. Whether or not we actually are our bodies, and whether they are anything besides our perceptions of them are questions that the various solutions disagree on. Therefore, I do not include these characteristics in the definition of the body at this point.

Physical and Non-physical

The physical has been defined as whatever is explainable by, or reducible, to physics. Although this definition might tell us a truth about the physical, it is an improper definition, for it does not capture the fundamental characteristic of the physical. To realize this, consider that the ability to be known by physics does not make possible any other physical characteristic. To find the fundamental characteristic of the physical, we must find out which characteristic of the physical makes it possible for the physical to be known by physics-- and which makes possible the other characteristics of the physical.

The characteristic that makes the others possible is objective existence. Nothing can be known by physics unless it objectively exists to be known. Nothing can be subject to natural law unless it is something on its own, not just something in a mind. Since objective identity is the fundamental characteristic of the physical, we can say that something is physical if and only if it exists and has an objective identity.

Something has an objective identity if its essence does not depend upon what any mind believes its essence is. There are two ways that this is possible. The first is that it could exist, in which case what can be known about it will be known through experience. The second is that its essence could follow from its definition. For instance, the definition of a triangle as a three- sided closed figure implies everything else that can be known about what a triangle is.

A subclass of objective identity is epistemological identity. The epistemological identity of something consists in a description of those characteristics of something that make a certain concept apply to it. The epistemological identity of any given triangle as a triangle, for example, includes only its triangularity. It does not include the measurements of the sides or angles. The epistemological identity of a belief consists in that which makes it a belief, not the neuron firings that may make up the belief.

In contrast to objective identity, there is subjective identity. Something has subjective identity if its essence depends upon what some mind (or minds) believes its essence is. Superman2, for example, has a subjective identity. His identity originally depended upon Siegel's and Shuster's conception of him, and it now depends upon the conception that his current writers and editors have of him. It is important to note that something must be an object of a belief to have subjective identity. A belief itself does not have a subjective identity unless its identity depends upon some other belief about it.

Now that you know the difference between objective and subjective identity, I can state more precisely what it means to be physical. Something is physical if and only if it exists, and it is what it is independently from what any mind whatsoever believes it is. We can see that this is indeed what the physical is when we consider that it is precisely what the immaterialists reject. Immaterialism does not deny that physics has any use; it denies that anything exists outside a mind.

Now that we know what physical means, we can say what non-physical means. Something is non-physical if it has objective identity but does not exist, or if it has subjective identity regardless of whether it exists. Circles and other geometric figures fall into the first category; fictional characters fall into the second.

The Mind

The fundamental characteristic of mind is the ability to have beliefs. A mind is aware of a world, which could be real or a dream, and it has beliefs about that world. Feelings are beliefs about the value of different things. Hopes and desires require the existence of beliefs.

A mind is more than a mere automaton that takes in information about a world and reacts to it. As I type in this sentence, my computer takes in information about the movements of my fingers, and it reacts to this information by storing certain information in its memory and by sending certain signals to my monitor, but it does not have a mind. It has no beliefs about my fingers, nor any hopes or feelings about them. A mind, however, will have beliefs and hopes and feelings about the world it is conscious of--even if it is completely incapable of acting on them. For example, I would like to soar through the sky like Superman, but I can't. My computer, though, has no such aspirations.

It is important here that the concept of the mind not be confused with the concept of an agent. Although minds might very well be agents, the concepts are different. An agent is what controls the body. There is no requirement in the definition of an agent that it be a mind. A body could conceivably be controlled by a data- processing device that reacts to the world without having any beliefs about it--not even in a metaphorical sense. The insect-like robot Attila (Freedman, Discover, 1991), for example, walks around and avoids stuff without even having a map of the area.

Another point that I must make here (because my advisor seems to think otherwise) is that the term "mind" is more than a convenient expression that has a place in some idioms. There is a real concept behind the word "mind," and that concept may not be lightly dismissed. When my advisor says something like "You have an intelligent mind," he regards it as nothing more than a behavioral expression about how well you can perform certain tasks. This is a functionalist definition of mind, and it is the wrong one. When I discuss whether minds exist, I will be discussing whether the concept behind my use of the word applies to anything. I will not be discussing whether there are any legitimate metaphorical uses of the word. Despite my advisor's protests that he has legitimate uses for the word, he does not believe in minds, for he does not believe that there is a legitimate, objectively definable concept behind the word.

The Meanings of the Four Propositions

Besides knowing what the terms in the tetrad mean, it is also important that we know exactly what the propositions in the tetrad mean. Therefore, I will define some propositional functions, and then translate the tetrad into symbolic logic. Let Px = x is physical, Mx = x is a mind, Bx = x is a body, and Ixy = x influences y. In terms of these functions, the tetrad looks like this:

T1(1) - (/\x) (Bx -> Px)

T1(2) - (/\x) (Mx -> ~Px)

T1(3) - (\/xy) [(Bx & My) & (Ixy & Iyx)]

T1(4) - (/\xy) [(Px & ~Py) -> ~(Ixy & Iyx)]

An explanation of these translations may now be in order. T1(1) will be true for any solution that denies the existence of bodies, and for any solution that affirms the existence of bodies and says that they are all physical. It will be false for any theory that says that bodies are non-physical. T1(2) will be true for any solution that denies the existence of minds, and for any solution that says that minds exist but are non-physical. It will be true for any solution that says that minds are physical. T1(3) will be false for any theory that denies the existence of bodies, the existence of minds, or that bodies and minds interact. T1(4) will be true for any theory that denies the existence of either the physical or the non-physical. The following proof will show this.

1. [(/\x) (~Px)] v [(/\x) (Px)]

2. ~Pa v Pb U.I. 1

3. ~Pa v ~~Pb D.N. 2

4. ~(Pa & ~Pb) De.M. 3

5. ~(Pa & ~Pb) v ~(Iab & Iba) Add. 4

6. (Pa & ~Pb) -> ~(Iab & Iba) Impl. 5

7. (/\xy) [(Px & ~Py) -> ~(Ixy & Iyx)] U.G. 6

It is also important to note that the consequent in T1(4) is a conjunction. This means that it will be true only when both conjuncts are true. So, T1(4) is asserting that there is reciprocal influence.

Now that we know what the terms mean, and precisely what logical relationship each proposition says exists between the terms, we can see more clearly the problem that the tetrad poses for us. Not only are the four propositions incompatible, but many people have found reason to believe each one. The first three all seem to be part of our experience, and the fourth seems to be a matter of common sense.

Why Each Proposition Seems Plausible

T1(1): Bodies are Physical

One of the first things that we discover about our bodies is that they have limitations that we cannot think away. Our bodies seem to be what they are no matter what we think about them. Although you can change your body by changing your body image, you will never have a super-powerful body like Superman has by thinking that you do. There seem to be facts about our bodies that our minds can't change. Thus, our bodies seem to exist and be what they are independently from what any mind thinks they are. It seems that our bodies are physical, for our bodies do not change with our every change in belief about them. If someone takes drugs, for example, and subsequently believes that he can fly like Superman, he will kill himself if he jumps off the roof of a skyscraper. Furthermore, our bodies seem to be affected by things that take our minds by surprise. If you aren't paying attention, a falling safe could kill your body before your mind has any idea of what is happening. Finally, there are many things that we do not know about our bodies, which seems to indicate that they are more than whatever we think they are.

T1(2): Minds are Non-physical

It may seem as though minds are non- physical, for thoughts do not seem to have anything in common with anything else we call physical. For example, a board is extended in space, but the thought of a board does not seem to be extended in space. An anvil is heavy, but we can't say that a mental image of an anvil is heavy. We can locate a radio wave, but nobody has yet located a thought. Also, we can describe many things with physics, but so far, nobody has reduced psychology to physics.

T1(3): Minds and Bodies Interact

It seems that the mind and body interact, for you can think of something that you want to do, such as type the words in a sentence, and then have your body do it. Also, it is through your sense organs, which are a part of your body, that you are conscious of the world about you. Furthermore, any of your mental attributes can be affected by the state of your body. A chemical imbalance in your brain can make you unhappy. Hunger or fatigue can make you irritable or draw your mind off of deep philosophical problems. Exercising your body can make your mind more active and better able to think.

T1(4): The Physical and Non-physical Cannot Interact

Finally, it would seem that the physical and non-physical cannot interact. The problem here is not one of conflict with experience, but one of conceivability. If the physical and non- physical have nothing in common with each other, as many are apt to believe, then it is difficult, if not impossible, to conceive how they could interact with each other. Furthermore, some even believe that physical interaction with the non-physical would violate the second law of thermodynamics.

The Related Problem of Free Will

Although this tetrad adequately captures the mind/body problem, I wish to present another one, which will shed a different light on the problem. One of the problems that has made the mind/body problem so intractable is the related problem of free will. This problem is captured by the following incompatible tetrad:

1 - Bodies are subject to natural law.

2 - Agents are self-determining.

3 - An agent is one with its body.

4 - Nothing subject to natural law is self- determining.

If we let Ax = x is an agent, Nx = x is subject to natural law, and Sx = x is self- determining, we can symbolize it as follows:

T2(1) - (/\x) (Bx -> Nx)

T2(2) - (/\x) (Ax -> Sx)

T2(3) - (\/x) (Bx & Ax)

T2(4) - (/\x) (Nx -> ~Sx)

The problem of free will is related to the mind/body problem, because any solution to the mind/body problem will leave unanswered certain questions about the mind/body relationship if it does not also have a position on free will. If, for instance, the mind and body interact, how do they interact? Therefore, a complete solution to the mind/body problem must also answer the problem of free-will. Like T1, this tetrad also poses a problem because we have reasons for believing all four propositions.

Why Each Proposition Seems Plausible

T2(1): Bodies are Subject to Natural Law

Our bodies seem subject to natural law, for they can be acted upon in predictable ways. We know that a person who cuts himself will bleed, that a person who exercises will be stronger, and that many other things will affect the body.

T2(2): Agents are Self-Determining

In our experience as agents, it seems that we determine what we do on our own. If there are outside forces that determine each word that I will write for this thesis, I do not find myself aware of being compelled by them. The same goes for my other decisions. In each case, it seems that I make my own decisions.

T2(3): An Agent is One with Its Body

It seems that agents are identical to their bodies, for the experience of astral projection is uncommon, and there is no scientific evidence for astral projection. Most people experience themselves as nothing more than their bodies.

Furthermore, whatever controls the body controls it by means of electrical and chemical signals. When these signals are interfered with, an agent has less control over its body. For example, an injury to the spinal cord often causes paralysis. If an agent were a separate entity that controlled the body by telekinesis, then injury wouldn't cause paralysis.

T2(4): Nothing Subject to Natural Law is Self-Determining

Finally, the idea that something that is subject to natural law can be self-determining seems to fly in the face of scientific knowledge. Some hold that neuroscience has had such success in explaining how the brain works that it seems likely that it will eventually explain all about how the brain works. But if the entire behavior of the brain can be predicted from a knowledge of natural law, it seems that it cannot also be self-determining. Moreover, natural science has not come up with any proof that there is free- will. Although quantum mechanics has found indeterminacy at the sub-atomic level, this has so far seemed to be better evidence for chance than for self-determination.

1. Throughout this paper, I shall use "physical" synonymously with "material." I shall use "matter" to mean physical stuff. I shall not, however, use "Materialism" synonymously with "Physicalism."

2. Whenever I refer to Superman in this paper, I will mean the DC comic book superhero, not Nietzsche's Übermensch.

Fergus Duniho / fdnh@troi.cc.rochester.edu