Cartesian Doctrine, also known as the mind-body dualism, or simple dualism in philosophy, is the concept that the mind and the body are two separate kinds of substance. The word Cartesian is derived from its source, French philosopher and mathematician Rene Descartes, who is also known as the father of modern philosophy.
The Cartesian doctrine states that the mind or consciousness belongs to a different plane of existence as the body, and therefore the two cannot be held in the same regard. According to the Cartesian doctrine, the mind belongs in the spiritual realm and therefore cannot affect the body, which belongs to the physical or material realm. The mind is thought to be acting independently from the brain, and activities that included ‘knowing’ was a function of the spirit or soul, including intelligence, thinking and sensing.
It was believed that the realm of the soul could not be touched by science. A scientific and mathematical approach was only possible for the physical or material world. This separation of mind and body enabled a lot of scientists at the time to divorce themselves from the restrictions of the church, paving the way for many scientific and philosophical breakthroughs at the time.