The Twin Earth thought experiment was proposed by the philosopher Hilary Putnam in his papers "Meaning and Reference" (1973) and "The Meaning of Meaning" (1975) to illustrate his argument for semantic externalism, the view that the meanings of words are not purely a matter of what is inside a speaker's mind. It was one of three cases Putnam offered in support of that view, alongside what he called the aluminum-molybdenum case and the beech-elm case, and it has since prompted numerous variations from other philosophers working on meaning and reference.
Facts
Origin YearSourced to the subject's own accountMarks Putnams earlier 1973 paper Meaning and Reference; the fuller treatment appeared in his 1975 paper The Meaning of Meaning. Classification
Position KindSourced to the subject's own account Sources
1. Twin Earth Thought Experiment (Wikipedia)
WikipediaTwin Earth (Wikipedia), on Putnam 1973 and 1975
Twin Earth is a thought experiment proposed by philosopher Hilary Putnam in his papers Meaning and Reference (1973) and The Meaning of Meaning (1975).
Twin Earth (Wikipedia), introduction
Twin Earth is a thought experiment proposed by philosopher Hilary Putnam in his papers Meaning and Reference (1973) and The Meaning of Meaning (1975).
View the Source Dissenting Readings (1 dissenting reading)
Description
Burge's mental content variance objection: the thought experiment is usually read as holding the twins' internal mental states fixed while their words' reference varies; Burge argues instead that Oscar has the concept H2O while Twin Oscar has the concept XYZ, so their mental states differ from the start, undercutting the claim that identical psychology can still yield different meaning.
A dissenting reading, from Tyler BurgeTwin Earth Thought Experiment (Wikipedia), Wikipedia
Frequently Asked Questions
Does the Twin Earth thought experiment show that two people can think identical thoughts but mean different things?
That was Putnam's own reading (meanings are not purely in the head), but Tyler Burge argued the twins' mental states already differ, since one genuinely has the concept H2O and the other XYZ.
Putnam used the thought experiment to argue for semantic externalism, summed up in his own phrase that "meanings just ain't in the head": two speakers can be molecule-for-molecule identical inside their own skulls and still mean different things by the same word, because meaning depends on the substance actually present in each speaker's environment. Tyler Burge's objection challenges the premise behind that reading: he holds that Oscar (on Earth) has the concept H2O while Twin Oscar (on Twin Earth) has the concept XYZ, so their mental states were never really identical to begin with, which changes what the thought experiment can be taken to prove about meaning versus about mental content.
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