Counterpart theory

Concept in metaphysics and philosophy In philosophy, specifically in the area of metaphysics, counterpart theory (CT) is an alternative to standard (Kripkean) possible-worlds semantics for interpreting quantified modal logic. Counterpart theory still presupposes possible worlds, but differs in certain important respects from the Kripkean view. The form of the theory most commonly cited was developed by David Lewis, first in a paper and later in his book On the Plurality of Worlds. Differences from the Kripkean view Counterpart theory (CT), as formulated by Lewis, requires that individuals exist in only one world. According to the standard account of possible worlds, a modal statement about an individual (e.g., "it is possible that x is y") says that there is a possible world, W, where the individual x has the property y; in this case there is only one individual, x, at issue. By contrast, according to counterpart theory, this statement says that there is a possible world, W, wherein exists an individual that is not x itself, but rather a distinct individual 'x' different from but nonetheless similar to x. So, when I state that I might have been a banker (rather than a philosopher),