Dualism
Dualism is a prominent theory in the field of philosophy that proposes two distinct substances or realms exist. This duality exists on many levels, including physical and mental aspects of reality as well as spiritual matters. The most common form of dualism is Cartesian dualism, proposed by the philosopher Rene Descartes (1596–1650). According to this theory, the universe consists of two distinct elements: res extensa (extended matter) and res cogitans (thinking substance). These two components are thought to be mutually exclusive; neither one can be reduced to the other. Res extensa includes all physical objects in existence while res cogitans encompasses consciousness, cognition, emotions, and free will—all things non-physical.
In addition to Cartesian dualism, there are also various religious forms of dualistic philosophies, such as Manichaeanism and Gnosticism, which posit an eternal battle between good and evil forces with God playing a pivotal role in their ultimate resolution. In some traditions, such as Hinduism, Buddhism, or Taoism, beliefs have been interpreted as being based upon principles of fundamental unity between body/mind or spirit/matter opposites rather than strict divisions between them—suggesting that both sides must coexist for true balance within nature itself. Finally, it’s important to note that not all philosophical theories embrace dualistic thinking; monists believe everything ultimately derives from one source, whether material or immaterial, depending on the school’s viewpoint.