Metaphysics - Chapter 9 (A)

(Originally written August 10, 2006 in Book 6)

Metaphysics - Peter van Inwagen

Chapter 9 - The Nature of Rational Beings: Dualism and Physicalism

Human Nature is a set of characteristics of rationality.

What makes humans capable of rationality? How is rationality realized? How is conscious experience realized? Answers to these questions are difficult to come by and belong to the field of philosophy of mind rather than metaphysics. Metaphysics can answer the question: what kind of thing is a human being? The answer to this will partially answer the previous questions.

What kind of thing is a human being? There are two seriously taken schools of thought today: 1) physicalism and 2) dualism.

Physical things are beings made up entirely of three elementary particles: up-quarks, down-quarks and electrons. Non-physical things are things not made up of any physical parts. Composite things are things made of both physical and non-physical parts.

Physical properties are properties possessed by physical things.

"The thesis the human persons are physical things is called physicalism" (van Inwagen, 151).

Physicalism is also a theory that the only individual things that exist are physical objects.

Dualism is the thesis that human beings are non-physical things.

Some idealists hold that there are only non-physical things.

Dualists believe that human beings have a dual nature. They hold that the person is a non-physical thing but its intimately connected with a physical human organism, the body.

How do the person of humans "x" and the human organism "x" interact?

Dualistic interactionism is one theory of how they interact. It states that the person X is in a 'cause and effect' relationship with organism X.

The account of the causal relations between person X and a certain organism X that make that organism person. X's body is dualistic interactionism. Dualistic interactionism holds that a person (non-physical) and its corresponding organism (physical) can affect one another.

Plato & Descartes were interactionists.

Some metaphysicians who are dualists reject dualistic interactionism because of the problems associated with a non-physical thing being able to effect a physical thing.

Descartes' follower Nicholas Malebranche proposed a theory called occasionalism. Occasionalism holds that when a person wills to do something with its physical body, God or some other being appropriates things to happen in the way a person wills it to. Changes in person or organism are to caused by each other. Changes are 'occasions'.

Another dualistic alternative to interactionism is 'epiphenomenalism'. Epiphenomenalism comes from the Greek word meaning 'by-product'. It holds that changes in a person can be caused directly by changes in a particular organism, but changes in the person never causes changes in that organism.

Dualistic interactionism does not demand that person can exist apart from its correlating organism.

Plato, an interactionist, believed that the soul (the person) would automatically continue to exist when its correlating body died. His argument for this was: the soul is a metaphysical simple and that a thing can only cease to exist by coming apart and since a soul is simple it cannot come apart.

Physicalists hold that the person is or is a part of the organism so they don't have any mind-body problems. Physicalists hold that emotions or any mental changes are merely changes of quarks and protons and how they are interacting.

The 'identity theory' is the theory that holds that emotions or mental changes are certain physical changes in the cerebral cortex.

Some philosophers and psychologists deny that mental changes take place altogether; i.e. behaviorism and eliminative physicalism.

The two most important theories about the nature of human beings are dualistic interactionism and physicalism (with the identity theory). Can either theory be proven or shown to be superior to the other?

Dualistic Arguments:
1. Descartes' Meditations on First Philosophy
-I can conceive of my body not existing
-I cannot conceive of myself not existing
-Thus, body and otherwise personhood are not the same
-Since personhood is not tied up with physical existence then personhood is not physical by nature.

Descartes' argument is flawed because he used the true principle. If 'X' has a property 'Y' lacks, then X is not identical with Y, but misapplied the term 'can be conceived by me not to exist' as a name of a property.

2. Another argument for dualism
- Physical things are incapable of thought and sensation
- Mental things are capable of thought and sensation
- Human persons are capable of thought and sensation
- Therefore, human persons are not physical things

Two questions arise from this argument
1) Why should we believe that physical things are incapable of thought and sensation?
2) What is a mental thing?

If physical things could have thoughts or feelings then we would be able to observe physical or material things like thoughts. We cannot however find these thought, thus there must be something other then a physical thing to hold thoughts: a mind or a mental thing.

Physicalists would agree that the physical things called thoughts are mysterious and we could not recognize them.

Thought and sensation are mysterious by nature and it does not matter whether you are a physicalist or a dualist, they are mysterious.

Since the dualist demands the existence of non-physical things and the physicalist demands the existence of physical things (that are equally unknowable or mysterious as non-physical things) it would seem that the dualist faces more challenges than the physicalist.

Another argument for dualism consists of supposing that there exists a rational being that is physically radically different to us. This is entirely possible. Thus, a being that is rational is therefore similar to humans but since it needn't posses a similar brain then physicalism seems to fail.

If physicalism is true then our physical brain mysteriously produces physical thoughts. But, if there theoretically exists a rational being physically dissimilar to us then how can a physical phenomena produce thought? Physicalists would argue stating, can there really be a rational being that differs so radically from humans? Then a proponent of this argument could argue that type-token distinction can prove that it is hypothetically possible for a rational being to exist that is radically different from humans. [A type is an event, i.e. death. A token is a particular type, i.e. Lincoln's death]. Thus by examining the type: death, and various tokens of of death: Lincoln, Caesar, My Grandad (Ed Linehan), Princess Di. My Grandad's death was from natural causes (heart failure). Princess Di's death was from a car wreck. Lincoln and Caesar were assassinated. All four are tokens of the type death. But Lincoln and Caesar are also tokens of the type assassination. A person can argue that rationality is thus a type and man's rationality is therefore a token of a type.

Type-Type physicalism claims that every mental event-type is identical to a physical event-type. Type-Type physicalism is such a strong thesis that few physicalists accept it.

Token-Token physicalism claims that each concrete mental event is identical with a concrete physical event, a particular change in the physical state of someone's brain.

Dualism can account for the "so-called identity of the person across time". Physicalism cannot. If physicalism is true then each human is a hunk of matter, a certain assemblage of atoms or elementary particles. But, no human being is the exact same hunk of matter he or she was ten years ago. This makes physicalism seem absurd.

Dualists do not face this problem because they hold the the human person is a metaphysical simple, a thing without parts.

Physicalists will sometimes state that a human person existing over time with a personal identity is merely a fiction used to make explanations easier. They maintain that no one who existed ten years ago exists today but we can say that they do for simplicity's sake.

Some physicalist philosophers offer "psychological continuity theories of personal identity" stating that the hunk of matter composing person X ten years ago causally created memories that the hunk of matter composing person X today now carries.

No matter what thought, causal relations cannot connect two completely different hunks of matter without a distorted view of identity or how things persist through time.

Proponents of psychological continuity must make a strange assumption about identity or how things persist in time. Those that do not are inconsistent. (A strange assumption is not equal to an absurd assumption. Physics is full of strange assumptions).

The first assumption is that there is no such thing as identity. The relativity of identity theory can state that X is the same person as Y, but X is not the same combination of matter as Y. By using the relativity of identity theory, physicalists can state that a person is the same through time because the way that the person's mental properties now have evolved from the person's mental properties ten years ago causally.

The second assumption is that human beings are not 3-D things that persist through time, human beings are 4-D things that are extended in time.

Some philosophers hold that in addition to the 3-D region of space that every human occupies the y also occupy a region along the space-time lne.

Four-dimensionalism does not therefore have to rely on the relativity of identity theory, they merely have to state that the person X ten years ago is a part of the same person (though a different one) that exists currently.

In essence a person exists in dimensions we don't always see. The person exists over a span of space-time but in our 3-D world we only observe the part that exists at that very moment.

Four dimensionalists hold that no atom is a part of a human only that a part of an atom was a part of a particular human at some point in time. Four dimensionalists believe though that we are composed entirely of atoms, but they have difficulty because in reality they state, "each momentary three-dimensional cross section of me is composed entirely of momentary cross sections of atoms" (van Inwagen, 174).