thought, language of See MEANING, MENTALESE,. PHILOSOPHY OF LANGUAG. thought experiment, a technique for testing a hypothesis by imagining a situation and what would be said about it (or more rarely, happen in it). This technique is often used by philosophers to argue for (or against) a hypothesis about the meaning or applicability of a concept. For example, Locke imagined a switch of minds between a prince and a cobbler as a way to argue that personal identity is based on continuity of memory, not continuity of the body. To argue for the relativity of simultaneity, Einstein imagined two observers – one on a train, the other beside it – who observed lightning bolts. And according to some scholars, Galileo only imagined the experiment of tying two five-pound weights together with a fine string in order to argue that heavier bodies do not fall faster. Thought experiments of this last type are rare because they can be used only when one is thoroughly familiar with the outcome of the imagined situation. J.A.K.