The thought experiment is known as “Twin Earth” was created to establish semantic externalism. Putnam uses the example of asking individuals to think of an isolated planet the same as earth, but instead of water (H2O), it has a different chemical substance (XYZ) that tastes like water and can be found in twin earth’s oceans and rivers (Lau). Nonetheless, if someone on earth identified the “water” on twin earth as H2O and not XYZ, then according to externalists the statement would be false (Lau). The experiment goes to show that certain beliefs do not apply to essential facts and therefore proving that externalism is true. Works Cited: Lau, Joe, and Max Deutsch. “Externalism About Mental Content.” Stanford Encyclopedia of Philosophy, Stanford University, 21 Oct. 2002, plato.stanford.edu/entries/content-externalism/.
