Dualism is a philosophical concept that posits the existence of two fundamental and distinct substances or realities. In the context of mind and body, it suggests that the mind is non-physical and separate from the physical body. This idea is often associated with the work of philosopher René Descartes, who argued that mental phenomena cannot be fully explained by physical processes. In addition to mind-body dualism, there are other forms of dualism, such as moral dualism, which contrasts good and evil as opposing forces. Dualism can also be found in various religious and spiritual beliefs, where two opposing principles, like light and darkness, are seen as fundamental to understanding the universe.