Varieties of Materialism 30 September & 2 October, 2002

Drs. Deutsch and Mallon

(1) Dualism seems untenable, and so we are left with the project of accounting for mental properties among material properties?

(2) Type physicalism or reductive physicalism:

Mental properties just are physical properties.

For example, perhaps:

Pain= C-fiber stimulation

Depression=Low Serotonin Levels

Cases of ‘a posteriori’ theoretical identification are common in science. For example, for tens of thousands of years, people have known about water, but only with the advent of modern chemistry did people acquire the belief that:

water=H₂0

Perhaps advances in brain science will teach us similar equivalences for brain state terms.

(3) Problem: We seem prepared to apply mental state terms to beings with very different physical organizations.

These include:

(a) Artificially intelligent robots

(b) alien beings

(c) animals

(d) humans with alternative physiologies

(e) ‘dualistic humans’- i.e. humans of whom dualism is true

While we want to connect the mental and physical, we need a dependence that is less strong than the identification of mental types with physical types. Perhaps we could use:

(4) Supervenience: no change in mental properties without some change in physical properties.

This has the advantage of not excluding alternate physical bases for mental states, but nonetheless requiring that the mental has a physical basis. But why would supervenience be the case? Why would this dependence hold? Materialists want to say something more, like, the physical determines the mental. But exactly how is that?

(5) Let’s reconsider type physicalism. Type physicalism holds that the mental state types or properties are identical to physical state types or properties. However properties (or types) are things individual objects have. For example,

I have the following properties:

(a) I live on Lamma Island.

(b) I teach philosophy.

One and the same individual (or token) has these types. Perhaps we can think of the relationship between the mental and physical in the same way? Call this token physicalism.

E.g. One and the same individual has the properties of, e.g.

(c) Being a pain.

(d) Being a C-fiber stimulation.

This does not identify the properties (any more than the previous example identifies the properties of living on Lamma Island with teaching philosophy). Thus it is a break with type physicalism. But it suggests that the same object has both.

(6) What is the Relationship Between Mental and Physical Properties?

Problem: We still don’t know about what the relationship between mental and physical properties is. There is, for example, no particular relationship between living on Lamma Island and teaching philosophy. But in the case of the mind it seems we need something more - we need to understand how it is that the physical properties are related to the mental properties.

To suggest, as we did above, that the mental is supervenient on the physical, tells us a bit more about the character of this dependence, but it still doesn’t tell us why the physical determines the mental.

(7) Functionalism:

Perhaps we can ask the question in another way, i.e. how are mental and physical properties related?

One popular view in philosophy is given by functionalism: the view that a mental state concept or term specifies a functional or causal role. For example, we might identify a pain with characteristic causes of pain, and characteristic resultant mental states and behaviors.

Then, according to functionalism, to be a mental state of a particular type is simply to play the causal role appropriate to that type. So, to go back to our examples earlier, what makes the computer’s belief that it’s raining, the alien’s belief that it’s raining, the animal’s belief that it’s raining, the human’s belief that it’s raining, and the dualist person’s belief that it’s raining all of the same type (i.e. all beliefs that it is raining) is that the various states in each of these creatures play the right causal role. E.g. they all are disposed to think this when it is in fact raining, and they all have characteristic responses.

(8) Three doctrines of nonreductive physicalism:

Token identity: mental state tokens are identical with physical state tokens

Supervenience: mental state properties are dependent on physical state properties.

Functionalism: mental state properties determine roles played by physical states.

(9) Problems

(a) Functionalism is too liberal. It allows mental states not only to the computer and the alien but any physical object with the right organization.

(b) The problem of causal exclusion. We want to know how the mental fits into the physical world. Dualism suffered from the problem of causal exclusion. It looks like mental state types, functionally construed, do as well.