Twin Earth thought experiment
Twin Earth is a thought experiment proposed by philosopher Hilary Putnam in his papers "Meaning and Reference" (1973) and "The Meaning of 'Meaning'" (1975). It is meant to serve as an illustration of his argument for semantic externalism, or the view that the meanings of words are not purely psychological. The Twin Earth thought experiment was one of three examples that Putnam offered in support of semantic externalism, the other two being what he called the Aluminum-Molybdenum case and the Beech-Elm case. Since the publication of these cases, numerous variations on the thought experiment have been proposed by philosophers.
The Twin Earth thought experiment posits a second Earth which is identical in all ways except one
A thought experiment is a hypothetical situation in which a hypothesis, theory, or principle is laid out for the purpose of thinking through its consequences. The concept is also referred to as a Gedankenexperiment within the work of Ernst Mach and includes thoughts about what may have occurred if a different course of action were taken as opposed to what did in fact occur. The importance of this ability is that it allows us to imagine what may occur in the future, as well as the implication of alternate courses of action.
Temporal representation of a prefactual thought experiment
Temporal representation of a counterfactual thought experiment
Temporal representation of a semifactual thought experiment
Temporal representation of prediction, forecasting and nowcasting