René Descartes: Philosophy, Metaphysics, and the Mind-Body Problem
René Descartes (1596-1650): A Foundation of Modern Philosophy
The *Cogito* and Cartesian Philosophy
René Descartes’ philosophy centers on the principle of Cogito, ergo sum (“I think, therefore I am”). This foundational concept is necessary to justify a principle of the whole demonstration (axiom). Descartes defines substance as something concrete and existing, characterized by independent existence, needing nothing other than itself to exist. He distinguishes between infinite substance (God) and finite substance (everything else, which requires God to exist). This leads to a soul-body dualism.
An attribute constitutes the essence of a substance. Each substance has a single attribute. For the soul, the attribute is thought (res cogitans), and for the body, it is extension (res extensa). Modes are various forms of a substance. The infinite substance (God) possesses the idea of perfection, which cannot be fictional or adventitious (derived from the senses) because neither Descartes nor the world is perfect. Therefore, this idea is innate, placed within him by a perfect God. The idea of God is evidence, and God cannot deceive us. God serves as the guarantee of the existence of other substances and is the first mover of the world.
Metaphysical Meditations and Principles of Philosophy
Descartes published Metaphysical Meditations in 1641. This work expands on the fourth part of his Discourse on the Method, discussing metaphysics, the self, and the substance of God. In 1647, Descartes wrote Principles of Philosophy, where he uses an anthology to make a comparison between his philosophical system and a tree (the Tree of Philosophy). The roots represent metaphysics (first principles), the trunk represents the study of physical and material things, and the branches represent medicine (care for human ills), mechanics (release from physical effort), and morality (directing human behavior). The Meditations focuses on the roots (knowledge of God, the distinction between body and soul, and innate ideas). It is divided into a destructive part (attempting to destroy unjustified beliefs) and a constructive part (attempting to remove doubts and develop a secure system of knowledge).
Meditations: Detailed Analysis
- First Meditation (Methodical Doubt and the Destructive Part): Descartes doubts everything to reach truth (V). His intention is to overcome skeptical doubts. Any idea that can be false (F) is considered unproven. He revises all beliefs through the senses and reason, employing moderate doubt (senses sometimes deceive) and hyperbolic doubt (the argument of sleep versus reality, suggesting a deceiving God). This leads to the conclusion that if he doubts, thinks, dreams, and is mistaken, he must exist. This is the first undoubted truth (V).
- Second Meditation (First Truth and the Doctrine of Substance): The first truth is clear and distinct. The essence of material reality is thought. Therefore, the mind is a substance that can exist without the body (dualism). An example is wax, whose essence is manner, place, and change or movement. Res cogitans is the thinking substance, and material things are res extensa, with the essence of extension (shape, location, and change or movement).
- Third Meditation (Existence of God as the Cause of the First Truth): If Descartes exists and thinks, the qualities outside of his mind are primary qualities. A picture represents something. There are three types: adventitious (originating from sensation and external to the mind), fictitious (originating from imagination and internal, produced and modifiable by the individual), and innate (originating from innate reason, unchangeable, such as mathematical notions, the idea of oneself as a thinking thing, and the idea of God). Volition is an act of will, and trials are the acceptance or rejection of a truth.
- Fourth Meditation (Removal of Doubts and the Cause of Errors): If God exists, why do we make mistakes? Descartes removes hyperbolic doubt by affirming God’s perfection. Errors arise from the sources of knowledge: understanding (the ability to intuit clearly and distinctly) and will (the ability to decide on the truth or falsehood of knowledge). Errors occur when the will exceeds the understanding.
- Fifth Meditation (Mathematical Knowledge and the Ontological Proof of God’s Existence): The innate idea of the body comes from Descartes himself, and as an extensive substance, it is understood in three dimensions. The ontological argument posits that God’s existence is a necessary positive quality of an infinitely perfect substance. The idea of God is the first order in metaphysical knowledge, guaranteeing other knowledge.
- Sixth Meditation (Proof of the Material World from Sensations, Dualism, and Reality versus Dreams): Truth is the coincidence of thought and reality, guaranteed by God, who places innate ideas of matter and motion within us. The understanding can construct “a priori” the structure of the physical world without mathematics needing to refer to experience. Sensible ideas must have a cause, which cannot be God or another higher being, as they would deceive us. Therefore, sensations are caused by material objects, proving the world’s existence.
Historical Context and the Scientific Revolution
Descartes lived during the Thirty Years’ War in the 17th century, a time of famine, pestilence, wars, and scientific discoveries. He is considered the father of modern philosophy, emphasizing human reason (rationalist anthropocentrism) and modern subjectivism, where the subject possesses evidence of knowledge. Rationalism breaks from scholasticism by focusing on reason rather than God (anthropocentrism versus theocentricism). Galileo’s physics emphasized efficient cause over final cause, leading to mechanism (the world as a machine) and the importance of mathematics. Descartes opposed the divine idea of the world, proposing a set of physical-mathematical ideas based on local movement. The laws of motion include the principle of inertia, the principle of conservation of quantity of movement, and the principle of rectilinear movement.
The Scientific Revolution during the Renaissance shifted the scientific model from geocentrism (Earth at the center) to heliocentrism (Sun at the center), with elliptical orbits, homogeneity of the universe, and the hypothesis of an infinite world. This involved a new methodology based on the hypothetico-deductive method, coordinating sensitive experiences with reason and mathematical proofs.
Rationalism and the *Discourse on the Method*
Rationalism emphasizes confidence in reason, contempt for sensitive knowledge, innatism (some things are self-evident), mathematics as a scientific model, and a focal method to understand the world. Descartes’ Discourse on the Method outlines his approach to knowledge. The work criticizes scholastic philosophy and proposes a provisional morality based on reason rather than religion or politics. Descartes asserts, “I think, therefore I am,” as an undeniable innate idea, establishing humans as thinking substances (mind-body dualism).
Plato’s Theory of Knowledge
Plato divided the world into the sensible world (accessed through the senses, yielding opinion) and the world of ideas (accessed through reason, yielding science). Humans are composed of body and soul. The body is tied to the sensible world, while the soul contains reason and is immortal. The soul existed in the world of ideas before joining the body and forgets its knowledge upon birth. The body becomes a prison for the soul, according to Pythagorean doctrine. Plato describes a process of liberation of the soul, where individuals recognize beauty and recall the ideas they once contemplated. This process, driven by Eros (love), involves purification and a return to the world of ideas. Knowledge, for Plato, is a reminiscence, a recovery of what the soul knew in the world of ideas. This process is both theoretical (gaining true knowledge) and practical (offering a specific style of life), positively affecting our lives.