René Descartes: A Deep Dive into His Philosophy
René Descartes: Life and Works
What we know about René Descartes’s life is that he was born in 1596 in La Haye (Touraine, France) into a comfortable family. Educated at the prestigious Jesuit college of La Flèche, he encountered the philosophies of Aristotle and St. Thomas, which he later deemed insufficient. During a stay in Holland, he met the scientist Isaac Beeckman, sparking an interest in physics and mathematics. He died in Stockholm in 1650, having been invited there by Queen Christina of Sweden.
His most notable works include Rules for the Direction of the Mind (1628), Discourse on the Method (1637), Meditations on First Philosophy (1641), Principles of Philosophy (1644), and The World or Treatise on Light, published posthumously.
Descartes’s Contributions to Science
Descartes was a key figure in the history of scientific thought. His well-known contributions include simplified algebraic notation; he created analytic geometry, laid the foundations of physical and biological determinism, and formulated theories about the nature of light and planetary movements. He also developed optical laws relating to reflection and refraction. His metaphysical developments are interpreted as complements or justifications for his scientific research, not as ends in themselves—a reaction to the revival of skepticism in modern times. His metaphysics links him more to the past, obscuring some aspects of his modernity. Descartes is modern in his conception of physics in mathematical terms, yet “old” in his reliance on God as the ultimate guarantor of knowledge.
Branches of Cartesianism
Cartesianism is divided into three main branches: The Christianized branch, stemming from Malebranche; the physics of Descartes, which remained the “official physics” in France until Newton’s triumph with the Enlightenment; and the spread of Cartesian thought throughout Catholic Europe by the Dutch philosopher Spinoza through his work, Principles of Philosophy. The German rationalist Leibniz offered critiques of Cartesianism in his Monadology. While not as comprehensive, his friend Huygens, perhaps the greatest achievement in philosophy, authored the Treatise on Light, establishing a wave theory of light that would be revived in the nineteenth century.
The Renaissance and its Impact
The revival and reform of the fifteenth and sixteenth centuries saw decisive changes in European society and culture. The Renaissance challenged medieval certainties, shifting from a medieval theological culture to a humanistic one. The fragmentation of Western Christendom from the sixteenth century onward, beginning with Luther’s Reformation, broke the established scholarship, moving from theocentrism to anthropocentrism, resulting in the modern world. Humanism revived interest in Greek philosophers, renewing classical ideas. Key features include human reason as a paramount principle, forming the foundation of scientific knowledge. The Renaissance revived ancient ideals, exalting individual dignity and emphasizing observation-based investigation of nature. In Italy, humanism flourished, with Petrarch and Marsilio Ficino (sixteenth century) translating Plato’s works into the vernacular. Outside Italy, figures like Nicolaus Cusanus, Erasmus of Rotterdam, and Thomas More (Utopia) contributed to this movement. Two significant events impacted humanity: the crisis and division of Western Christianity (Protestant Reformation) and a profound crisis and revolution in science, particularly in astronomy with Copernicus. During the sixteenth century, the Church faced a schism, with Luther, Calvin, and Zwingli reinterpreting the Bible, emphasizing individual religious experience and consciousness, and rejecting the need for intermediaries between God and humanity. The Church lost power, and new scientific theories emerged, initiating the scientific revolution and the modern world (1543: Copernicus’s On the Revolutions of the Heavenly Spheres, arguing for a heliocentric model). Initially dismissed, this theory gradually gained acceptance through testing and observation. Copernicanism clashed with the Church, contradicting sacred texts, leading to its ban in 1616. It also presented scientific challenges, necessitating a physics compatible with a mobile Earth (Galileo), and Kepler’s correction of the circular orbit theory. The Church’s attempts to suppress Copernicanism ultimately proved futile.
Rationalism, Empiricism, and the Scientific Revolution
The linkage of rationalism and empiricism with the scientific revolution saw the heliocentric theory displace Earth and humanity from the center of creation. Coupled with the religious crisis and the failure of Aristotelian physics, the sixteenth century in Europe witnessed a resurgence of skepticism (Pierre Charron, Michel de Montaigne’s Essais). Magic and science were conflated, as seen in figures like Giordano Bruno, Campanella, and Paracelsus. Two closely related yet opposing trends countered this skepticism. Rationalism, prevalent in continental Europe in the seventeenth century, asserted that true knowledge derives from reason. All knowledge stems from innate ideas. Rationalists viewed mathematics as the epitome of sound knowledge. Knowledge should be deductive, starting from self-evident truths. Mathematical physics, crucial to the Scientific Revolution, and metaphysics were developed. Key figures include Descartes (French), Spinoza (Dutch), and Leibniz (German). Empiricism, developing in the British Isles, posited that all knowledge comes from experience and sensation. Empiricism is critical philosophy, highlighting the limits of human knowledge, criticizing metaphysics, theology, ethics, and similar disciplines. It considers scientific knowledge only probable. Francis Bacon, a key precursor, published his influential Novum Organum in 1620, advocating a new scientific method based on observation and proposing state-funded scientific societies that would revolutionize science (Royal Society). Later empiricists include Locke, Berkeley, and Hume. The scientific revolution resulted from the interplay of these philosophical trends, requiring the dismantling of Aristotelian theory and its worldview, a task impossible without the contributions of these thinkers.
Descartes’s Method
Descartes’s philosophy aimed to integrate the new science of nature (or natural philosophy) and propose a universal method for attaining truth. His first goal was to invent a valid method to avoid confusion. Mathematics served as his model. Descartes’s method involved two modes: Intuition, a kind of instinct or natural light by which we grasp simple concepts of reason beyond doubt or error (searching for self-evident truths whose denial is impossible, e.g., 2 + 2 = 4). These truths serve as reliable starting points needing no proof. Deduction involves deriving more complex truths from simple concepts grasped through intuition. The mathematical method of intuition and deduction leads to certain reasoning, ensuring the conclusion’s validity. Intuition and deduction were among the rules Descartes proposed as a true method of philosophy.
The four rules of his method are: 1. The rule of evidence: only accept what is indubitable; 2. The rule of analysis: reduce complex ideas to simple ones; 3. The rule of synthesis: reconstruct knowledge from simple ideas; and 4. The rule of enumeration and review: ensure nothing is overlooked. Discovering self-evident truths is essential; they are the starting point of his method, aiming to distinguish truth from falsehood. By following these rules, the entire edifice of knowledge can be built without error.
Methodical Doubt
Methodical doubt involves analyzing all prior knowledge and reality to identify truths. The scope of doubt can be: 1. Universal, doubting all truths and philosophical principles, sensory experiences, and the existence of a self as a subject of knowledge; 2. Methodological, serving as a constructive tool for error-free thought; and 3. Theoretical, concerning statements, not actions, affecting theory, not beliefs. Descartes applied this method, maintaining a “moral status” to prevent it from becoming destructive. The first reason to doubt knowledge lies in the fallibility of the senses. A second reason is the doubt about the existence of external reality. A third concerns reasoning itself—errors in reasoning are possible, even in mathematics. Descartes introduces the concept of an omnipotent evil genius who deceives humanity, blurring the line between reality and fiction, making everything subject to doubt. Yet, something remains indubitable: the existence of the thinking subject and the act of doubting itself. This is the Cogito ergo sum: “I think, therefore I am.” The Cogito is the starting point for deducing all other truths. Whatever is perceived with equal clarity and distinction is real. The Cogito is a clear and distinct idea.
Ideas and their Classification
Descartes deduces the existence of external reality from the Cogito. The objects of thought are ideas, classified as: 1. Adventitious ideas, seemingly originating from the senses; 2. Factitious ideas, created by the imagination; and 3. Innate ideas, present in the mind from its inception. Descartes considers the idea of God crucial, guaranteeing our knowledge and the existence of an external world.
The Idea of Infinity
Descartes emphasizes the idea of infinity, identified with the idea of God. This idea does not originate from the senses, and he attempts to prove it is not factitious. He argues that the very conception of finitude implies the idea of infinity, which he equates with God. From this, he deduces God’s existence. His arguments include: 1. The ontological argument, influenced by Anselm and Aquinas; and 2. A causal argument, demonstrating God’s existence through the concept of infinity. The existence of the external world is demonstrated through God’s existence: God’s infinite goodness precludes deception regarding the external world, therefore, the external world exists. God guarantees the correspondence between our ideas and the external world, ensuring the certainty of knowledge.
Structure of Reality
Descartes distinguishes three areas forming the structure of reality: 1. God (infinite substance); 2. The self (thinking substance); and 3. Bodies of the physical world (extended substance). These are finite and infinite substances, self-caused and caused by others. Each substance is identified by an attribute equivalent to its essence (perfection for God, thought for the self, and extension for bodies). Substances have modes expressing how they are. The concepts of attribute and substance were critically examined by English empiricists. The bodies of the external world are the fundamental object of his thought.
Mind-Body Problem
The problem of communication between substances arises from Descartes’s distinction between the three substances. This is discussed in his Meditations on First Philosophy (1641) and Principles of Philosophy (1644), addressing how different substances relate. The mind-body problem remained unresolved. Cartesian metaphysics posits that we exist as thinking things; the mind is easier to understand than the body. Thought can exist without the body because a substance, as defined by rationalists, does not require anything else to exist; thinking substance equals soul. Descartes considered the mind and body two self-sufficient substances, raising the question of their union. He proposed the pineal gland in the brain as the point of union between thinking and extended substances. Rationalists strongly criticized this position. Spinoza argued that Descartes’s solution lacked clarity, maintaining that reality consists of a single substance, and mind and body are merely two ways of perceiving it (attributes). Leibniz proposed that bodies are composed of numerous simple substances.