Mind
Drs. Deutsch and Mallon
1. A widely known thought experiment regarding ‘twin earth’ has convinced many philosophers that content or meaning is determined, in part, by factors outside an individual. In particular, what an individual means is not entirely determined by their beliefs.
In the experiment, we are to imagine a ‘Twin Earth’ exactly like Earth, except on Twin Earth instead of H20, there is another substance with the chemical formula XYZ. XYZ has all the same superficial properties as H20, but a different underlying structure. Denizens of both Earth and Twin Earth use the word ‘water’. The intuition of the thought experiments is that an Earthling means H20 by ‘water’ while a Twin Earthling means XYZ.
2. Hilary Putnam, author of the Twin Earth example, suggests that when we use certain kinds of terms (including names and ‘natural kind’ terms), we mean to pick out the underlying stuff or underlying essence of the thing we label.
This is not true of all terms. E.g. the term ‘skateboard’ picks out a certain kind of device, regardless of where the device is. In the case of a skateboard, there is no ‘underlying difference’ picked out by the term or concept. So, the word ‘skateboard’ as used on Earth would apply to a skateboard on Twin Earth.
3. The theory proposed to explain the phenomenon is that some terms or concepts express the essential properties of the thing that the term or concept was introduced to label. E.g. what makes ‘water’ mean H20 on Earth is that ‘water’ was introduced in order to label stuff with the underlying essence H20. On Twin Earth ‘water’ means XYZ for similar reasons.
4. The same theory holds of names. A name picks out a particular person, the person for whom the name was introduced, rather than a person who just happens to meet the description associated with the name.
5. The points about meaning and content apply equally well to words and to thoughts. If meanings of words are not in the head, the meanings of concepts are not either.
6. Perhaps least controversially, externalism is true with indexical terms - terms like ‘here’, ‘now’, and ‘I’. These terms pick out different things in different contexts of utterance. Or, to put it another way, what these terms mean depends on where, when, and by whom they are uttered.
7. Externalism about content has been widely seen to raise serious and perplexing difficulties. Here are a few:
I. Explanatory
failure of folk psychology
Folk psychology is the widely employed ordinary theory that people use to explain and predict the behavior of others by reference to prepositional attitudes. These attitudes, remember, involve a relation to a proposition. The main thing here is that propositions have their meaning and content essentially, and so do propositional attiudes. What makes Tom’s believe that the Earth is round the belief that it is is that it has the content the Earth is round.
But, according to externalism, that content is determined in part by the context in which Tom finds himself. So, 1.
(i) Content is externally determined.
Add to this,
(ii) Folk psychology explains by invoking content.
Why believe ii? Folk psychology explains Tom’s behavior by reference to his beliefs and desires. But these beliefs and desires are individuated by reference to their content.
However, it seems independently plausible to assert:
(iii) A person’s behavior is caused by their brain and body states. I.e. a person’s behavior is explained by facts that are ‘inside the skin’.
Since externalism would have it that Tom’s belief is not entirely ‘in the head’. Thus, we might conclude:
(a) Folk psychological states are not really explanatory. They are epiphenomenal because the contents figure in them play no role in the causation of behavior.
Some philosophers (like Stephen Stich (1982) have accepted this consequence, and they have sought to focus on an alternative, scientific psychology that would invoke only narrow states. Other philosophers (e.g. Ned Block) have thought that we could think of these narrow states as having a kind of narrow (as opposed to wide) content.
Alternatively, we could conclude that.
(b) iii is false. A person’s behavior is not to be explained by reference to their brain and body states.
It’s worth thinking about which horn of the dilemma we should take, if we accept externalism.
II. Failure of self knowledge
As McGinn also notes, externalism also seems to have the consequence that we don’t know the content of our own beliefs. That is, it turns out a person may not know what they themselves mean.
Consider a famous example, due to Tyler Burge, in which a man goes to his doctor with a pain in his knee. The man believes
(a) arthritis is a disease of the joints and limbs.
(b) I have arthritis in my knee.
The doctor, upon visiting with the man, confirms that his knee pain is caused by arthritis. But he also points out that arthritis is never a disease of the limbs. The term refers only to a disease of the joints.
It seems natural to think that the man would conclude that, “I didn’t know the meaning of arthritis.” However, the man was able to pick out the disease perfectly well, despite his false belief about the meaning of ‘arthritis’. (In fact, his belief was true). It seems like this is a case of a man not know what he meant by his own words and thoughts.
III. A reply to skepticism?
There is a long tradition in philosophy of entertaining skeptical hypotheses. As we saw when we considered Descartes ‘argument from doubt’ for dualism, this kind of skepticism can be a valuable tool in clarifying what the essential character of a thing is.
However, Hilary Putnam has suggested that externalism about meaning suggests a way in which such skepticism is nonsensical. Putnam reasons as follows: suppose you were a brain in a vat, and your current experiences are actually being fed into your brain by a serious of electrodes connected to a computer run by a mad scientists. Then,
(1) By externalism, your thoughts and concepts would be about the things that cause them.
(2) So, when you, say, thought about having some water, your thoughts would be thoughts about electrical impulses.
(3) Thoughts like, “if I go to the store, I will be able to buy some water to quench my thirst” will turn out to be true! That is because the terms - e.g. ‘store’ and ‘water’ - pick out complexes of electrical impulses, and your thought will be true of those impulses.
Hence (4) you would not really be deceived.
If Putnam is correct, skepticism is not quite as coherent as we had imagined.