Descartes’ Philosophy: Method and Ontology

Posted on Oct 17, 2024 in Philosophy and ethics

1. Introduction

René Descartes, a prominent 17th-century philosopher, developed a complex philosophical system encompassing method, metaphysics, anthropology, scientific advancements, and religious and theological concerns. He engaged with theologians, philosophers, and scientists throughout Europe, often critically. In 1619, he envisioned a rigorous method for constructing science and metaphysics. His key works include Rules for the Direction of the Mind, Discourse on Method, Meditations on First Philosophy, Principles of Philosophy, and The Passions of the Soul.

2. Descartes’ Method

Descartes’ primary philosophical objective was discovering and justifying a method based on the unity and simplicity of human reason, applicable to all knowledge domains. The need for a philosophical method emerged during the Renaissance and was later emphasized by Bacon. With Descartes, the pursuit of a method ensuring the same certainty as mathematics became paramount. He aimed to achieve absolute truth, eliminating any possibility of error. Descartes believed that knowledge is clear, accessible, and attainable through proper reasoning and method.

Descartes’ method, a tool for invention and discovery, allows deduction of further truths from an initial, intuitively grasped truth, building a solid philosophical structure. This method is accessible to anyone possessing reason and good sense.

2.1 Rules of the Method

Descartes stated, “I understand by the rules of a method certain and easy precepts, such that by observing them accurately, one will never take what is false for true, and, without unnecessarily wasting mental effort, but by gradually and constantly increasing one’s knowledge, will arrive at a true understanding of everything within one’s capacity.” The method should lead safely and easily to true knowledge, encompassing the world and the wisdom of life. Discourse on Method outlines four rules:

Evidence: Accept as true only what is clear and distinct, leaving no room for doubt. Intuition is the act by which the mind achieves evidence (Descartes defines intuition as “a conception of a pure and attentive mind, so easy and distinct that no doubt remains about what we understand; or, what amounts to the same thing, a conception of a pure and attentive mind, which proceeds solely from the light of reason”). Intuition is the mind perceiving its own concepts, becoming transparent to itself. Clear (present and manifest to the mind) and distinct (separated from other ideas, containing nothing belonging to others) ideas are key.
Analysis: Divide complex ideas into simpler ones. Descartes states, “divide each of the difficulties under examination into as many parts as possible, and as many as were required to solve them in the best way.”
Synthesis/Ordering: Proceed from simple to complex ideas. Descartes advises, “conduct my thoughts in such order that, by commencing with objects the simplest and easiest to know, I might ascend by little and little, and, as it were, step by step, to the knowledge of the more complex.”
Enumeration: Review and list the entire process to ensure completeness, including all necessary and sufficient elements for problem resolution. Descartes states, “In every case make enumerations so complete, and reviews so general, that I might be assured that nothing was omitted.”

Descartes believed that analysis and synthesis, responding to reason’s internal dynamics, are not arbitrary but the only valid method. While previously used primarily in mathematics, he advocated for their application in all knowledge areas.

3. Cartesian Ontology

Descartes presented his ontology in three expositions, consistently addressing the following:

Methodical doubt concerning material things and the certainty of mathematics.
Certainty of “I think, therefore I am” as the first evident truth.
Demonstration of God’s existence.
God’s existence as a guarantee for judgments based on clear and distinct ideas.
The soul’s essence as thought.
The body’s essence as extension.
Certainty of the existence of material things.

3.1 Methodological Doubt

Descartes believed that achieving certain knowledge requires eliminating all uncertain ideas and beliefs. His doubt was:

Universal: Questioning all existing certainties.
Theoretical: Limited to philosophical reflection, not extending to ethical beliefs or behaviors.
Methodical: A tool for philosophical development, not an end in itself.

Descartes doubted:

The senses: As they can deceive.
The external world: Due to the difficulty of distinguishing dreams from reality.
Reasoning: Suggesting God might deceive us (“perhaps God has willed that I should be deceived, even in matters that seem most evident”).
Himself: Positing the possibility of an evil spirit causing error.

3.2 The First Truth

Descartes arrived at an undeniable truth: the existence of the thinking subject. Doubting implies existence as a thinking being. This is expressed in his famous phrase, “I think, therefore I am,” derived from mental intuition. This truth serves as the foundation for his criteria of certainty: anything perceived with equal clarity and distinctness must be true.

3.3 Ideas

Descartes believed thought always involves ideas. Unlike previous philosophers, he argued that thought does not directly grasp things but rather ideas (a representational theory of knowledge). He distinguished two aspects of ideas: mental acts (modes of thought) and objective content. He identified three types of ideas:

Adventitious: Seemingly derived from external experience (though the external world’s existence was yet to be proven).
Factitious: Constructed by the mind from other ideas.
Innate: Inherent to thought itself (e.g., ideas of thought and existence, derived from the perception of “I think, therefore I am”). These ideas serve as the basis for demonstrating external reality and provide objective knowledge.

Rationalism, as exemplified by Descartes, is a representational theory of knowledge, understanding knowledge as representations within the mind.

3.4 The Existence of God

Descartes offered three arguments for God’s existence, two based on the principle of causality (every effect has a cause) and a posteriori reasoning. The first posits God as the only possible cause of our idea of infinity, while the second presents God as the only possible cause of our being (as we would have made ourselves perfect if we could have). The third argument asserts God’s existence as contained within the idea of perfection. Unlike St. Thomas Aquinas’ arguments, Descartes’ rely on clear and distinct ideas, not sensory experience.

God’s existence and attributes of veracity and immutability serve to demonstrate the existence of the physical world. Since God cannot deceive (as deception is an imperfection), our mind’s “natural light” is trustworthy. God’s goodness also implies that he would not deceive us into believing in a non-existent world, therefore the world exists.

God guarantees the existence of a world constructed from extension and motion, from which physics can be deduced.

3.5 Substance

Descartes asserted the existence of three substances (substance being that which exists independently):

Thinking substance (res cogitans or I): Identified with the soul or self. Its attribute is thought, with modes of willing, feeling, imagining, and judging. Thought is distinct from and independent of the body. This leads to a mind-body dualism, defending human freedom by liberating the soul from a mechanistic worldview.
Infinite substance (res infinita): Identified with God, whose attribute is perfection.
Extended substance (res extensa): Corporeal substance. Its attribute is extension, with modes of figure, position, and motion. This substance is infinitely divisible, inert, and determined by mechanical movements affecting individual bodies (modes of extended substance). Nature consists of all extended substance, governed by laws apprehensible by reason. Physics reduces to mechanics, ultimately becoming mathematics. Space and matter are identified.