An Earthling and their Twin Earth duplicate are in exactly identical brain states when they think 'water is refreshing.' On Twin Earth, the liquid called 'water' is XYZ, not H₂O. According to wide content externalism, which of the following is true?
AThey have the same thought, since their brain states are identical and content is fully determined by brain states
BThey have different thoughts: the Earthling's thought is about H₂O, the Twin-Earther's thought is about XYZ, despite identical brain states
CThey have the same thought, since both are thinking about a substance with identical functional and experiential properties
DThe question is unanswerable — content cannot be compared between people with different causal histories
Wide content externalism holds that content is partly fixed by the environment and causal history, not by intrinsic brain states alone. The Earthling's causal-historical connection is to H₂O, so 'water' in their thought refers to H₂O. The Twin-Earther's causal history is with XYZ, so their thought refers to XYZ. Despite identical internal states, the thoughts have different contents — they are about different things. This is Putnam's central result: 'meanings just ain't in the head.'
Question 2 Multiple Choice
Before the discovery of molecular chemistry in 1750, an Earthling and their Twin Earth counterpart were in identical brain states when thinking 'water.' What does Putnam's externalism say about their concepts at that time?
ATheir concepts were the same in 1750 because neither knew the molecular structure of their respective liquids
BTheir concepts were different even in 1750, because reference is fixed by the actual causal-historical connection to the substance, not by what the thinker knows about it
CTheir concepts were the same because conceptual content is determined by functional role, which was identical for both H₂O and XYZ
DThis is a counterexample to externalism — in 1750 the external environment was irrelevant to content since molecular structure was unknown
Externalism holds that reference is fixed by the actual causal connection to the substance, not by the thinker's knowledge of its nature. Even in 1750, the Earthling's term 'water' referred to H₂O because their wells, rivers, and rain were H₂O — regardless of their ignorance of chemistry. The Twin-Earther's term referred to XYZ for the same reason. The discovery of H₂O did not change the reference; it revealed what the reference had been all along. Reference does not wait on the thinker's knowledge of the essence.
Question 3 True / False
Wide content externalism implies that two people in identical brain states can have thoughts with different propositional contents.
TTrue
FFalse
Answer: True
This is the central claim of externalism, illustrated directly by the Twin Earth argument. The Earthling and Twin-Earther are stipulated to be in identical brain states yet think about different things (H₂O vs. XYZ). Their thoughts differ in content despite no internal difference. This is what makes the view externalist: part of what determines thought content lies outside the thinker, in their environment and causal history.
Question 4 True / False
Wide content externalism entails that introspection is substantially unreliable — since mental states are partly constituted by external factors, we can seldom have any direct knowledge of what our own thoughts are about.
TTrue
FFalse
Answer: False
Externalism raises questions about the limits of introspective access to referential content — if you cannot know by introspection alone whether you are on Earth or Twin Earth, you cannot be certain by introspection alone what 'water' in your thoughts refers to. But this is not the same as introspection being completely unreliable. Introspection reliably tracks many features of mental states: that you are having a thought, that it concerns water-like stuff, its phenomenal character. Externalism challenges the completeness of introspective access to reference, not all introspective reports.
Question 5 Short Answer
Explain why the internalist position — that mental content is entirely fixed by intrinsic brain states — conflicts with our intuitions about the Twin Earth case. What does Putnam mean by 'meanings just ain't in the head'?
Think about your answer, then reveal below.
Model answer: Internalism predicts that identical brain states must produce thoughts with identical content. But the Twin Earth case generates the intuition that the Earthling's 'water' thought and the Twin-Earther's 'water' thought differ in content — one is about H₂O, the other about XYZ — despite identical brain states. The internal state cannot explain this difference because it is the same in both cases. What differs is each person's actual causal-historical relationship to the substance in their world. 'Meanings just ain't in the head' captures this: the content of 'water' is not fixed by any description or mental image inside the thinker, but by which substance in the world the thinker and their linguistic community are actually causally connected to.
The philosophical significance is that if content is partly external, then purely internal accounts of the mind — including narrow functionalism — fail to individuate mental states in the way our ordinary talk about beliefs and desires requires. This has implications for mental causation, self-knowledge, and the scientific study of mind.