What is the Twin Earth thought experiment?

Proposed by philosopher Hilary Putnam in the 1970s, the Twin Earth thought experiment illustrates semantic externalism. It demonstrates that the meanings of our words are not determined purely by what is inside our heads. Instead, external factors and environments help shape what we mean when we speak.

What we know

• The Twin Earth thought experiment was proposed by philosopher Hilary Putnam in papers published in 1973 and 1975. [1, 2]
• The thought experiment serves as an illustration of Hilary Putnam's argument for semantic externalism. [2]
• Semantic externalism is the view that the meanings of words are not purely psychological. [2]
• The Twin Earth case was one of three examples offered by Putnam, alongside the Aluminum-Molybdenum case and the Beech-Elm case. [2]

Where to go next

• whoWho was philosopher Hilary Putnam?
• the bigger pictureWhat is semantic externalism?
• a case in pointWhat are the Aluminum-Molybdenum and Beech-Elm cases?
• how it workedHow do thought experiments test philosophical theories?
• what followedHow have other philosophers varied the Twin Earth scenario?
• an unexpected connectionHow do electricity cables share a name with a planet-doubling thought experiment?Both concepts make use of the descriptive label Twin and Earth, though one refers to a philosophical puzzle about meaning while the other designates a standard electrical wiring cable used in buildings.

Sources

• [1]Twin Earth thought experiment (Wikidata Q244774) · CC0 1.0
• [2]Twin Earth thought experiment · CC BY-SA 4.0
• [3]Thought experiment · CC BY-SA 4.0
• [4]Twin Earth · CC BY-SA 4.0
• [5]Multiverse · CC BY-SA 4.0