Dualism and Epistemology: Descartes vs. Plato
Anthropological Dualism in Descartes and Plato
Descartes: The Radical Dualism of Substance
Descartes defines substance as that which contains within itself the cause of its own existence. He differentiates between an absolute substance (God, who is omnipotent and infinite) and two finite substances: res extensa (extension) and res cogitans (thought). Between these two, there is no communication; they are independent substances that possess attributes and modes. These features can only be conceived if the substance itself is conceived, as it serves as an unconditional basis with an independent reality.
This radical dualism applies to man, who is seen as an accidental union of both thought and extension, corresponding to the soul and the body. The body's movement is justified by its composition as fragments of matter (aligned with analytic geometry and the circulatory system), while the soul possesses the intellect, the will, and therefore, freedom.
Plato: The Body as a Prison
Plato's conception of the soul as a substance radically distinct from the body is rooted in his Theory of Ideas. He introduces a radical dualism where the body belongs to the world of the senses. Plato distinguishes three parts of the soul:
- The rational soul
- The irascible soul
- The concupiscible soul
Given this framework, the body is viewed as the prison of the soul, and death signifies the soul's salvation and liberation.
Epistemology and the Theory of Knowledge
Descartes and the Rationalist Method
Descartes is a primary representative of rationalism, subjecting sensory data to rational knowledge. The data of experience has no value unless it follows a rational order and a rigorous method. Through methodological doubt and specific rules, one arrives at ideas that are clear and obvious, and therefore true. An idea is a mental act—a thought content—rather than just a thing dependent on what it represents.
Descartes posits nativism, focusing on three primary ideas: the Self, God, and the World. Through these, he affirms external reality based on the attributes of res extensa and res cogitans (movement), which act upon modes or accidents.
Plato: The Hierarchy of Ideas and Anamnesis
For Plato, what truly exists are the Ideas; every Idea is a reality. These Ideas are perfect and do not reach full fruition within the sensible field. The real world contains the Forms of physical beings and mathematical concepts. These hierarchical Ideas culminate in the Idea of Good.
Thus, Plato's conception of reality follows a radically dualistic pattern, distinguishing between:
- Ideas (The realm of true knowledge, episteme, and science)
- Physical beings (The realm of opinion or doxa)
True knowledge is reached by ascending through specific stages. This promotion toward absolute and total knowledge is known as the dialectic. In contrast, sentient beings merely imitate Ideas, and they do so poorly. Therefore, Plato argues that learning is remembering (anamnesis), because the soul already possesses the knowledge of all Ideas within itself.