Dualism (Indian philosophy)
Dualism in Indian philosophy refers to the belief held by certain schools of Indian philosophy that reality is fundamentally composed of two parts. This mainly takes the form of either mind-matter dualism in Buddhist philosophy or consciousness-matter dualism in the Samkhya and Yoga schools of Hindu philosophy. These can be contrasted with mind-body dualism in Western philosophy of mind, but also have similarities with it.
Twin Earth thought experiment
Twin Earth is a thought experiment by philosopher Hilary Putnam, first in his paper "Meaning and Reference" (1973), and then in his paper "The Meaning of 'Meaning (1975), to illustrate his argument for semantic externalism, or the view that the meanings of words are ultimately not purely psychological. The "Twin Earth" thought experiment was one of three, the other two being the "Aluminum-Molybdenum", and the "Beech-Elm" cases. Since the publication of these cases, philosophers have proposed numerous variations on the experiment.