Mental Content
With Reference to Jaegwon Kim, Philosophy of Mind, Third Edition, Chapter 8

Philosophy of Mind
Curtis Brown

Early on, we distinguished between phenomenal and intentional mental states. The previous chapter concerned (primarily) phenomenal states. This chapter concerns intentional ones. (Recall that "intentional" in this context just means "representational.")

We will see in the next chapter that phenomenal states (qualia) pose at least a prima facie problem for physicalism (the "hard problem" of consciousness).

Intentional (representational) states, i.e. states with content, seem to pose a different kind of problem (or at least question) for physicalism: where, on a physicalist account, does mental content come from? How is it that mental states can have contents at all? If we think about the natural world, it doesn't seem to contain any intrinsic "aboutness," or what Searle calls "intrinsic intentionality." So if humans are just complex natural organisms, what is it about their states that gives them representational content?

First Issue: In What Does Mental Content Consist? (By virtue of what natural properties do our mental states have contents?)

Notice that the question here is not what causes mental content, but what constitutes it. Questions like this can seem somewhat mysterious, but they are not unique to philosophy; lots of physical laws are also constitutive rather than causal. (F = ma, but it's not that having a certain mass and acceleration causes an object to have a certain force; rather, force just is the product of mass and acceleration. Something similar is true for the ideal gas law and various other physical laws.

Possible answers to the question:

1. Interpretivism: states don't intrinsically have content. Rather, the process of interpretation endows them with content. So the content of my beliefs is just whatever the best interpretation says it is; there is no deeper fact about content. One problem with this view is that it seems to lead to circularity or an infinite regress. If I am to interpret your states as having content, then my own mental states must already have content. If the content of my states, too, simply comes from their interpretation, it's not clear where the original content could come from.

2. The causal-correlational approach. The main idea here is that a mental state has as its content a certain external phenomenon if and only if the state covaries with the phenomenon.

For instance, a certain perceptual state will have the content RED if and only if it is typically caused by red things, and typically is not caused by things that aren't red.

Problems: (1) This has some plausibility for perceptual states, that is, states that refer to directly observable phenomena. It doesn't seem to have any plausibility for states that are about other phenomena: for instance, abstract entities (numbers, sets); theoretical entities (electrons, force fields); or even observable things that we'll never have the opportunity to observe (dinosaurs). The account could still be correct for perceptual states, but if so, we need a way to extend it so as to explain the content of other states also.

(2) Even for perceptual states, if P and Q are reliably correlated, there seems to be no way to distinguish between a representation of P and a representation of Q.

(3) If representations represent whatever they are reliably correlated with, it's puzzling how we could ever misrepresent something. Suppose I have a perceptual state that is triggered by horses. But sometimes it also gets triggered by skinny cows in bad light. In that case, am I misrepresenting a cow as a horse? Or is my representation just a horse-or-skinny-cow-in-bad-light representation?

3. The teleological approach. This can be regarded as a way to solve problems (2) and (3) above. The idea is that a mental representation represents something if it is the function of the representation to indicate that thing. How do things acquire functions? Two ways: in the case of artifacts, they are deliberately designed to function in a certain way: so a certain mark on a thermometer represents 100 degrees F because that's what it was designed to represent. Second, in the case of organisms, by virtue of natural selection. If the reason we have a certain representation is because its correlation with P helped our ancestors to survive and reproduce, then it represents P.

Note that the teleological approach (at least in the biological version) only seems to help with representations that are innate. So it can't be a complete account of mental representation, but perhaps it can give an account of basic cases and then we can understand more complex cases as defined in terms of the simple ones.

Second Issue: Are Mental Contents Broad or Narrow (or Both)?

Broad vs. Narrow

A property (or state, etc.) is narrow if and only if it supervenes on the intrinsic properties of the thing which has it. A property is broad if and only if it is not narrow, i.e. if and only if it does not supervene on the intrinsic properties of the thing which has it. (It might still supervene on the individual-plus-environment combination.)

It's hard to give a precise definition of an intrinsic property, but roughly it's a property of an individual that doesn't depend on anything other than that individual. In the case of organisms, it's a property of the organism that depends only on characteristics of the organism from the skin inward. Thus an intrinsic property of an individual must be shared by any exact duplicate of that individual, while an extrinsic property will not necessarily be shared by all duplicates.

Example: weight is not intrinsic (because an exact duplicate of me on Mars would weigh less). Mass is (at least closer to being) intrinsic: my mass doesn't depend on which planet I happen to be on.

Another example: being female is intrinsic; being a sister is not. Having a certain volume is intrinsic; being 1800 miles from New York is not.

Background

Several pairs of terms which make more or less the same distinction:

intension	extension
meaning	reference
Sinn	Bedeutung

The extension of a term is the set of things of which it is true. So the extension of the term 'rabbit' is the set of all the rabbits in the world; the extension of 'blue' is the set of all the blue things; the extension of 'pets in Curtis Brown's household' is {Callie, Elsa}, and so on.

Obviously the extension of a term used by someone depends not just on that person's intrinsic properties, but also on his or her environment or context. (My wife could have acquired another pet today, in which case 'pets in Curtis Brown's household' now has an additional item in its extension.)

There has to be more to meaning than extension. Two expressions can have the same extension and yet differ in meaning: 'the Morning Star' and 'the Evening Star' both refer to Venus, but don't mean the same thing; similarly, 'number of sides of a triangle' and 'number of angles of a triangle' have the same extension (namely, the number three), but don't mean the same thing.

Intensions are often thought of as having two properties: (1) intensions determine extensions: the intension of a word or phrase is thought to determine which things it is true of. (2) grasping an intension, understanding the meaning of an expression, is a narrow psychological state.

What kind of thing could an intension be, if it were to satisfy these two conditions? One common idea is to think of an intension as being something like a set of necessary and sufficient conditions for being in the extension of an expression. So the intension of "triangle" might be something like: three-sided, closed, planar figure. Having three sides, being closed, being planar, and being a figure are all necessary conditions for being a triangle; and the conjunction of all of these necessary conditions gives us a sufficient condition for being a triangle. Similarly, the intension of "bachelor" might be something like: adult, unmarried male. Being an adult, being unmarried, and being male are all necessary conditions for being a bachelor, and their conjunction is a sufficient condition.

Putnam's Negative Thesis

The picture above can't be correct, according to Putnam. Narrow psychological state doesn't determine extension; therefore, at least one of the two links must be broken.

This thesis is negative, and is supported by examples that appear to show that two exact duplicates could refer to different things.

Example 1 (Twin Earth): Roll the clock back to 1750, and pretend that humans don't consist largely of water. Twin Earth is just like Earth, including having duplicates of all of us, except that wherever Earth as H2O, Twin Earth has a different colorless, odorless liquid, XYZ. When Oscar uses the word 'water', he refers to H2O; but when his exact duplicate Twin Oscar uses the word in his language that sounds just like 'water', he refers to XYZ.

Example 2 (arthritis): Peter thinks he has arthritis in his thigh. But you can't get arthritis in the thigh: it's a disease of the joints. (Obviously Peter is unaware of the linguistic fact that the word 'arthritis' refers to a disease exclusively of the joints.) But now consider Peter's exact duplicate in a counterfactual situation in which the word 'arthritis' is actually used more broadly to refer to any rheumatoid ailment. Duplicate Peter's belief, which he would express with the words "I have arthritis in my thigh," is true. (This example is due to Tyler Burge.)

Putnam's Positive Theses

Putnam offers two reasons for the failure of psychological state to determine reference.

1. The contribution of other people. I don't need to know how to identity what all my terms refer to as long as there are experts around who do. (I can use 'molybdenum' to refer to molybdenum even though I have no idea how to identify samples; I can use 'beech' to refer to beech trees, etc.) This is Putnam's thesis of the "linguistic division of labor." The arthritis example relies on this contribution.

2. The contribution of the environment. Putnam thinks that kinds of things have (or often have) a nature that isn't apparent to casual observation. It may be this hidden nature that determines what some of our expressions refer to, even if we don't (yet) know what this nature is. Most (not all) of Putnam's examples are "natural kind terms," like 'water', 'gold', 'tiger', etc. Where we thing things have a hidden nature we don't know, we often intend to use words to refer to whatever has the same nature as the samples around here. This is basically the thesis Putnam calls "the indexicality of reference." The Twin Earth example relies on this contribution.

Broad and Narrow Content

Putnam (and Burge) argue that all or nearly all mental content is broad. However, some have argued that there must be some contents that are narrow, and that these are more basic than the broad ones. As Kim notes, the thesis that all content is broad seems to give rise to problems about (a) mental causation, and (b) our apparently direct knowledge of our own mental states.