Cartesian Rationalism and the Foundations of Modern Philosophy

Posted on Nov 24, 2024 in Philosophy and ethics

Cartesian Rationalism in Modern Philosophy

1. Overview: The Rise of Rationalism

A) General Characteristics of Rationalism:

Emphasis on Subjective Knowledge: The thinking self is the fundamental reality, with everything rooted in subjectivity.
Systematic Thought: Rationalism constructs comprehensive systems of thought from first principles, deducing theorems and forming a global system through inference.
Logical-Deductive Method: Rationalism employs logical deduction as its primary method of inquiry.
Metaphysical Concerns: It addresses traditional metaphysical questions concerning God, the world, and the soul.
Autonomy of Reason: Rationalism prioritizes reason over dogma and faith (Deism).
Mathematical Method in Metaphysics: Rationalists apply the mathematical method, seeking apodictic certainties through rigorous logical deduction and the application of analytical geometry (Descartes).

B) Rationalism vs. Empiricism:

Rationalism and empiricism are the two dominant currents in modern philosophy, differing in their origins of knowledge:

Rationalism: True knowledge of reality originates from reason, leading to the acceptance of innate ideas.
Empiricism: All knowledge comes from sensory experience, rejecting innate ideas and positing the mind as a blank slate at birth.

Rationalists acknowledge sensory information but consider it confused and unreliable.

2. Descartes’ Philosophical Reflection

Philosophical Disappointment with Divided Ideas: Modern philosophy begins with an emphasis on subjective knowledge. While the division of ideas remains significant, Descartes proposes a unified conception of knowledge and reason, arguing that human wisdom is singular because reason is singular.

Descartes’ Dream: Reconciling Human Thought: In his Meditations on First Philosophy, Descartes envisioned a logical world structure and a unified science encompassing all knowledge. He sought to reconcile human thought and end the division of ideas, leading him to develop his method outlined in Discourse on the Method. This method draws inspiration from classical Aristotelian logic and the mathematical model.

3. The Cartesian Method (Epistemology)

3.1. Provisional Moral Rules

During his process of doubt, Descartes adopts temporary moral rules as a foundation for his ultimate morality:

Caution and Prudence: To minimize deviation from the correct path in case of error.
Treat the Likely as True: To avoid indecision.
Stoic Morality: Adapt desires to the world order to avoid wanting the unattainable and achieve contentment.
Cultivate Reason: Descartes examines various pursuits and chooses the cultivation of reason and the pursuit of truth as the best.

Descartes links happiness to knowledge, believing his method secures the acquisition of all attainable knowledge and the possession of all real goods within his reach.

3.2. The Search for a New Method

Sources of Inspiration: Classical Aristotelian logic and the mathematical model (algebra and geometry) aim to achieve the same level of certainty and agreement in philosophy as in mathematics.

Basic Attitudes Towards Knowledge:

Intuition: The natural light of reason grasping simple concepts directly.
Deduction: Connecting insights to derive further knowledge through logical inference.

Steps of the Method:

Evidence: Accept only clear and distinct ideas, rejecting anything doubtful. Evidence is found in intuition (the mind’s clear and immediate grasp of an idea), modeled after mathematical evidence. Ideas are mental concepts, not Platonic forms. Ideas of things are more important than the things themselves. Evidence is a property of ideas, not things. Clarity and distinction define evidence: an idea is clear when it is distinct from other ideas, and distinct when its parts are not confused. Avoid precipitation (accepting the untrue) and prevention (rejecting the obvious).
Analysis: Divide complex difficulties into their simplest parts (simple natures). Divide composite ideas into simple ideas to find evidence. Each simple nature is grasped by intuition.
Synthesis: Order thoughts logically, connecting and resolving the analyzed parts through deduction.
Enumeration (Review): Review the entire process to ensure completeness. An incomplete review jeopardizes the conclusion. The method’s accuracy depends on evidence: evidence of the first truth, evidence in the procedures, and evidence in the whole process.

Results and Assumptions: The method yields excellent results in mathematics, prompting Descartes to apply it to philosophy. He believes there are no mysteries and everything can be known through clear and distinct ideas (reducible to mathematical functions). Like surveyors, we should start with simple things and progress to complex issues. The method assumes: 1) reality consists of simple natures, 2) knowing is grasping simple natures, and 3) nativism (innate ideas).

3.3. Starting Point: Doubt to Overcome Skepticism

Meaning of Cartesian Doubt: Descartes doubts to find something indubitable. The purpose is to achieve certainty by overcoming skepticism.

Characteristics of Doubt: Universal (doubting all knowledge, including reality’s existence), real (not feigned), methodical (a tool for achieving certainty), and theoretical (not applied to ethics, accepting provisional moral standards).

Scope of Doubt:

Doubt of the Senses: Senses sometimes deceive, so why not always? Doubting perceived reality doesn’t negate its existence. Since doubt is universal, we must doubt reality’s existence.
Doubt of Reality’s Existence: We sometimes can’t distinguish waking from dreaming. Mathematical truths seem certain in both states, but they too must be doubted.
Doubt of Intelligence’s Ability: Understanding can err in reasoning, even in mathematical proofs. This leads to the hypothesis of an evil genius deceiving us in our pursuit of truth.

3.4. Overcoming Doubt and Skepticism: The First Truth

Cogito ergo sum: I cannot doubt that I doubt; therefore, to doubt, I must exist. I am a thinking being, thus an existing being. However, only inner activity (doubt, thought, feeling, imagination) is proven, not the body’s existence.

The Cogito as the First Truth: The clear and distinct idea of the thinking subject is the foundation of Descartes’ philosophy. It is the first truth, certain and evident. Anything perceived with equal clarity and distinction is true. The cogito (subject) is the basis of modern philosophy, inspired by St. Augustine “If I am mistaken, I a”). For Descartes, the cogito is the starting point of all reflection, while for St. Augustine, it is just another example of true things.

From Mental to Extra-Mental: Starting from doubt, we arrive at the existence of the thinking subject (mental). The challenge is to move from the mental to the extra-mental (reality), from subject to object.

4. Analysis and Classification of Ideas

4.1. The Problem of Reality’s Existence

We have the clear and distinct idea of the thinking subject, but how do we prove the existence of a reality external to thought? Descartes must deduce the existence of reality from the existence of thought, using thought and its ideas as elements for deduction.

4.2. The Concept of Idea

Descartes’ concept of idea differs from previous philosophy, which focused on things, not ideas. For Descartes, thought is about ideas, not things. The problem is ensuring the correspondence between the idea of the world and the reality of the world.

4.3. Nature of Ideas

Descartes distinguishes two aspects: as mental acts, all ideas are equally real and originate from thought; but in terms of objective content, each idea is different.

4.4. Classification of Ideas

Adventitious Ideas: Seemingly derived from external experience (senses).
Factitious Ideas: Created by imagination and will.
Innate Ideas: Inherent in thought itself, such as the ideas of thinking and existence. Descartes includes the idea of an infinite substance (God) as innate, guaranteeing the existence of external reality.

5. Metaphysics: Reality and God

Descartes views the self as a substance whose essence is to think. Substance is the concrete thing that exists.

5.1. Metaphysics of Substance

Concept of Substance: A thing that exists and needs only itself to exist.
Types of Substances: Infinite substance (God) needs nothing else to exist. Finite substances (res cogitans – thought, and res extensa – matter) need only God to exist. Substances have attributes (how we know them) and modes (their properties).

5.2. General Metaphysics: God (Natural Theology)

Descartes demonstrates God’s existence by analyzing innate ideas:

Ontological Argument (St. Anselm): The innate idea of God as the most perfect being implies his existence, as existence is a perfection. A supremely perfect being lacking existence wouldn’t be truly perfect.
Argument from Infinity: The innate idea of infinity must have an infinite cause, as the finite self cannot create it. Therefore, an infinite reality (God) exists.
Argument from Perfection: The idea of perfection cannot originate from imperfect beings like ourselves. It must be induced by a more perfect being possessing all perfections, i.e., God.

Attributes and Role of God: God’s essential attributes are infinity and perfection. God bridges the gap between self and the external world, solving the problem of reality. Since God exists and is perfect (and thus cannot deceive), the world must exist.

Special Metaphysics: The World (Cosmology) – Res Extensa (Matter)

Res Extensa: A finite substance needing only God to exist, independent of res cogitans (Cartesian dualism). Descartes argues that while his existence as a thinking self doesn’t prove his body’s existence, his powers and activities (movement) imply the existence of an extended substance.

Existence of the World: We perceive the world, bodies, and things with extension (length, width, depth), the attribute of corporeal substance. The truth of this idea comes from God. God’s existence and perfection guarantee the world’s existence.

Attribute of Body: The fundamental attribute of bodies is extension (quantifiable mathematically). Movement is also important due to its quantifiability.

Res Cogitans (Thinking Substance): Cartesian Anthropology

Cartesian Dualism: While certain of his thinking, Descartes doubts his body’s existence. What he doubts (his body) cannot be the same as what he doesn’t doubt (his thought). Thus, thought and body are distinct. Humans are composed of matter (extension) and spirit (thought), independent simple natures accidentally joined.

Mind-Body Interaction: Descartes proposes the pineal gland in the brain as the soul’s residence, facilitating interaction and communication between body and soul. This solution is weak. The objective of Cartesian dualism may be to preserve human freedom.