Piero Scaruffi(Copyright © 2013 Piero Scaruffi | Legal restrictions )
These are excerpts and elaborations from my book "The Nature of Consciousness"
Dualism And The Mind-Body Debate
Historically, two main schools of thought have antagonized each other: “dualism“ and “monism“.
According to dualism, mind and body are made of two different substances. The first and most famous of dualists was the French philosopher René Descartes, who is credited with starting the whole “mind-body debate” in 1649. He observed that reality is divided into matter and spirit. These are two different worlds, made of two different substances. He defined what matter is and what mind is: matter is whatever exhibits the property of "extension" (geometric properties such as "size", "shape", etc.) and mind is… "cogito", i.e. thought (a more scientific definition of mind would come later from Franz Brentano). "Res extensa" (things that have an extension) and "res cogitans" (things that think) belong to two separate realms, and cannot be studied with the same tools. This dualism had an enormous influence on future generations. Newton's Physics, for example, is a direct consequence of that approach: Physics studies the realm of matter, and only deals with matter. And such it would remain until the end of the 20th century.
Descartes' dualism was a departure from Aristotle's dualism that had ruled for centuries. Aristotle divided things into living and nonliving. Living beings behaved differently and therefore required a different treatment. Descartes realized that living and nonliving matter are, ultimately, the same matter, that obeys the same physical laws. There is "one" physical world for everything. Living matter appears to "behave" because it is more complex. In reality, animals are mechanical automata. The real distinction is at the level of thought. Some beings (and, for Descartes, it was only humans) can think. The difference is not between living and nonliving matter, which are ultimately the same substance, but between matter and mind, which are two different substances. In a sense, Aristotle's philosophy was centered on life, whereas Descartes' philosophy was centered on the human being. (It would take three centuries to resurrect the idea that animals, too, may have a mind, and therefore return to Aristotle). Descartes also understood that the brain must be the seat of the body-mind interaction, although he couldn't quite explain it.
The 18th century British philosopher David Hume was a dualist too, but he pointed out that "mind" is really a set of "perceptions". The self is an illusion. The mind is simply a theater where perceptions play their part in rapid succession, often intersect and combine. The self is like a republic, whose members have an independent life but are united by a common constitution: the republic is one, even if the members (and maybe even their individual constitutions) are continuously changing. The identity of the republic is provided not by its contents, that are continuously fluctuating, but by the causal relationship that holds its members together.
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