Twin Earth Argument

Last updated Dec 25, 2021 Edit Source

my twin is thinking of XYZ and I am thinking of H2O
XYZ ≠ H2O
content determines object (frege: the sense of a term determines its referent)
if t1 and t2 have different objects, then they must also have different content
twin and I have thoughts with different content
thoughts are individuated by their content
twin and I have different thoughts even though we are molecule-for-molecule duplicates
“the fact that an English speaker in 1750 might have called XYZ “water,” whereas she or his successors would not have called XYZ water in 1800 or 1850 does not mean that the “meaning” of ‘water’ changed for the average speaker in the interval

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