Modern Rationalism & Empiricism Skill

Master the early modern period (c. 1600-1800)—the age of the “epistemological turn” when philosophy focused on questions of knowledge, mind, and method, culminating in Kant’s critical synthesis.

Overview

The Epistemological Turn

Medieval Philosophy: What is real? (Metaphysics first) Modern Philosophy: What can we know? (Epistemology first)

Historical Context

SCIENTIFIC REVOLUTION (Background)
├── Copernicus (1473-1543): Heliocentrism
├── Galileo (1564-1642): Mathematical physics
├── Newton (1643-1727): Mechanics, calculus
└── New confidence in human reason

CONTINENTAL RATIONALISM
├── Descartes (1596-1650): Method, dualism
├── Spinoza (1632-1677): Monism, Ethics
└── Leibniz (1646-1716): Monads, pre-established harmony

BRITISH EMPIRICISM
├── Locke (1632-1704): Tabula rasa, ideas
├── Berkeley (1685-1753): Idealism
└── Hume (1711-1776): Skepticism, naturalism

SYNTHESIS
└── Kant (1724-1804): Transcendental idealism

Continental Rationalism

Core Commitments

Descartes (1596-1650)

The Method of Doubt:

CARTESIAN DOUBT
═══════════════

LEVEL 1: SENSES
├── Senses sometimes deceive (optical illusions)
├── Therefore, cannot trust senses completely
└── But this doesn't show everything from senses is false

LEVEL 2: DREAMING
├── I cannot distinguish dreaming from waking with certainty
├── Any sensory experience could be a dream
└── But even in dreams, mathematical truths hold

LEVEL 3: EVIL DEMON (Malin Génie)
├── Imagine a supremely powerful deceiver
├── Could make me wrong about everything
├── Even 2+2=4 could be implanted deception
└── Global, hyperbolic doubt

SURVIVING THE DOUBT:
"Cogito, ergo sum" — I think, therefore I am
├── Even if deceived, I must exist to be deceived
├── First certain truth
└── Foundation for rebuilding knowledge

Meditations Structure:

Mind-Body Dualism:

CARTESIAN DUALISM
═════════════════

MIND (Res Cogitans)         BODY (Res Extensa)
─────────────────           ─────────────────
Thinking substance          Extended substance
Unextended                  No thought
Indivisible                 Divisible
Free                        Mechanical
Known directly              Known through senses

INTERACTION PROBLEM:
How can unextended mind affect extended body?
Descartes: Pineal gland (unsatisfying)

Clear and Distinct Ideas:

• Criterion of truth: Whatever I perceive clearly and distinctly is true
• God guarantees this criterion (no deceiver)
• Circle? (Need God to validate criterion, criterion to prove God)

Spinoza (1632-1677)

Radical Monism: There is only ONE substance—God/Nature (Deus sive Natura)

SPINOZISTIC METAPHYSICS
═══════════════════════

SUBSTANCE
├── That which is in itself and conceived through itself
├── There can be only ONE substance (infinite, necessary)
├── = God = Nature
└── Has infinite attributes

ATTRIBUTES
├── What intellect perceives as constituting substance
├── We know two: Thought and Extension
├── Mind and body are same thing under different attributes
└── Parallelism, not interaction

MODES
├── Modifications of substance
├── Individual minds, bodies are modes
├── Finite, dependent, determined
└── All follow necessarily from God's nature

ETHICS
├── Freedom = understanding necessity
├── Highest good: intellectual love of God
├── Emotions: adequate vs. inadequate ideas
└── "Sub specie aeternitatis"

Determinism: Everything follows necessarily from God’s nature

• No free will in libertarian sense
• Freedom is acting from one’s own nature
• Knowledge liberates from bondage to passions

Leibniz (1646-1716)

Monads: Ultimate simple substances

LEIBNIZIAN MONADOLOGY
═════════════════════

MONADS
├── Simple substances, no parts
├── No windows (cannot be affected from outside)
├── Each contains whole universe from its perspective
├── Differ in clarity of perception
└── Hierarchy: bare → souls → spirits

PERCEPTION AND APPETITION
├── Each monad perceives entire universe
├── Most perceptions are "petites perceptions" (unconscious)
├── Appetition: internal drive from perception to perception
└── Mirrors the universe

PRE-ESTABLISHED HARMONY
├── Monads don't interact
├── God synchronized them at creation
├── Like two clocks keeping perfect time
└── Solves mind-body problem without interaction

PRINCIPLES
├── Identity of Indiscernibles: No two things exactly alike
├── Sufficient Reason: Nothing without a reason
├── Best of All Possible Worlds: God chose the best
└── Continuity: Nature makes no leaps

Theodicy: This is the best of all possible worlds

• God could create any logically possible world
• God chose the best (maximum perfection with minimum means)
• Evil exists because a world with evil can be better overall
• (Voltaire’s Candide satirizes this)

British Empiricism

Core Commitments

Locke (1632-1704)

Theory of Ideas:

LOCKEAN EPISTEMOLOGY
════════════════════

SOURCE OF IDEAS:

SENSATION                    REFLECTION
├── External world           ├── Operations of mind
├── Through senses           ├── Perception, memory, reasoning
└── Primary source           └── Secondary source

TYPES OF IDEAS:

SIMPLE IDEAS
├── Cannot be further analyzed
├── Passive reception from experience
├── Examples: yellow, cold, hard, sweet
└── Building blocks

COMPLEX IDEAS
├── Mind combines simple ideas
├── Three types:
│   ├── Modes (modifications)
│   ├── Substances (collections)
│   └── Relations (comparisons)
└── Examples: beauty, gratitude, army, causation

Primary and Secondary Qualities:

Personal Identity: Not same substance, but same consciousness

• Memory connects present to past self
• Identity follows consciousness, not substance
• Forensic concept (responsibility)

Berkeley (1685-1753)

Immaterialism: Esse est percipi (To be is to be perceived)

BERKELEYAN IDEALISM
═══════════════════

THE ARGUMENT:

1. We perceive only ideas (Locke agrees)

2. Ideas can only exist in a mind (perception requires perceiver)

3. Material substance is supposed to cause ideas

4. But we have no idea of material substance!
   └── Abstract idea of "matter" is incoherent

5. Therefore, "material substance" is meaningless

6. Objects = collections of ideas

7. What makes objects persist when unperceived?
   └── God perceives all things always

AGAINST LOCKE:
├── Primary/secondary distinction fails
├── All qualities are ideas, all ideas are mind-dependent
├── "Material substance" is an empty abstraction
└── Abstract ideas are impossible

God’s Role:

• God’s mind sustains all ideas
• Laws of nature = God’s regular perceptions
• Other minds: known by analogy, not perception

Hume (1711-1776)

Impressions and Ideas:

HUMEAN EPISTEMOLOGY
═══════════════════

IMPRESSIONS                  IDEAS
├── Lively, vivid            ├── Faint copies
├── Direct experience        ├── Derived from impressions
└── Original                 └── Copies

RELATIONS OF IDEAS           MATTERS OF FACT
├── Certain, necessary       ├── Contingent
├── Deny → contradiction     ├── Deny → no contradiction
├── Mathematics, logic       ├── Empirical claims
└── A priori                 └── A posteriori

HUME'S FORK:
Any claim either concerns:
1. Relations of ideas (analytic, certain)
2. Matters of fact (synthetic, probable)
If neither, "commit it to the flames"

The Problem of Induction:

HUME'S PROBLEM
══════════════

We reason: The sun has risen every day, therefore it will rise tomorrow.

But this assumes: Nature is uniform (future will resemble past)

How do we know this?
├── Not by reason alone (no contradiction in nature changing)
├── Not by experience (circular—uses induction to prove induction)
└── Not at all! Habit and custom, not reason.

SKEPTICAL SOLUTION:
├── Cannot justify induction rationally
├── We form expectations through habit
├── This is natural, unavoidable
└── Live by natural belief, not rational proof

Causation:

HUME ON CAUSATION
═════════════════

TRADITIONAL VIEW: Necessary connection between cause and effect

HUME'S ANALYSIS:
1. Constant conjunction (A always followed by B)
2. Contiguity in space and time
3. Temporal priority (A before B)

WHERE IS NECESSARY CONNECTION?
├── Not in objects (we see only succession)
├── Not in experience (no impression of necessity)
└── In the mind! (Habit creates expectation)

CONCLUSION:
├── Causation = regular succession + mental expectation
├── No real power in objects
└── "Necessary connection" is projection

Personal Identity:

• No impression of the self
• Self = bundle of perceptions
• “A kind of theatre where several perceptions make their appearance”
• Puzzlement: What ties the bundle together?

Kant’s Critical Synthesis

The Critical Project

Problem: How to preserve science while answering Hume’s skepticism?

Solution: Transcendental idealism

KANT'S COPERNICAN REVOLUTION
════════════════════════════

TRADITIONAL VIEW:
Mind conforms to objects
(We passively receive information about world as it is)

KANT'S REVOLUTION:
Objects conform to mind
(Mind actively structures experience)

CONSEQUENCE:
├── We can know phenomena (appearances)
├── Cannot know noumena (things-in-themselves)
├── Synthetic a priori knowledge is possible
└── Through forms supplied by the mind

Types of Judgment

KANT'S DISTINCTIONS
═══════════════════

                    ANALYTIC          SYNTHETIC
                    (Predicate in     (Predicate adds to
                     subject)          subject)

A PRIORI            "All bachelors    "7 + 5 = 12"
(Independent of     are unmarried"    "Every event has
 experience)        ✓ Everyone        a cause"
                    accepts           THE KEY QUESTION!

A POSTERIORI        (Impossible—      "The cat is on
(Dependent on       analytic truths    the mat"
 experience)        don't need        ✓ Everyone
                    experience)       accepts

The Central Question: How is synthetic a priori knowledge possible?

Transcendental Aesthetic (Space and Time)

SPACE AND TIME
══════════════

NOT:
├── Properties of things-in-themselves
├── Abstract concepts derived from experience
└── Relations between things

BUT:
├── Forms of sensible intuition
├── Structures the mind imposes on experience
├── A priori conditions for perception

SPACE
├── Form of outer sense
├── Makes geometry possible
└── Necessary, a priori

TIME
├── Form of inner sense
├── All representations in time
├── Makes arithmetic possible
└── Necessary, a priori

Transcendental Analytic (Categories)

The Categories: Pure concepts of understanding

THE TWELVE CATEGORIES
═════════════════════

QUANTITY              QUALITY
├── Unity             ├── Reality
├── Plurality         ├── Negation
└── Totality          └── Limitation

RELATION              MODALITY
├── Substance         ├── Possibility
├── Causality         ├── Actuality
└── Reciprocity       └── Necessity

APPLICATION:
├── Categories structure all experience
├── Cannot be derived from experience
├── But only apply within experience
└── No transcendent use (beyond experience)

Transcendental Deduction:

• How can categories (a priori) apply to experience (a posteriori)?
• Answer: The unity of consciousness requires categorical synthesis
• “I think” must be able to accompany all my representations
• Categories are conditions for unified experience

Transcendental Dialectic (Limits of Reason)

Transcendental Illusion: Reason tries to extend beyond experience

THE THREE IDEAS OF REASON
═════════════════════════

SOUL (Psychology)
├── Rational psychology claims to prove immortality
├── Paralogisms: invalid arguments about the self
└── "I think" ≠ substantial soul

WORLD (Cosmology)
├── Antinomies: contradictory conclusions
├── Thesis vs. Antithesis both provable
├── Example: World has beginning / No beginning
└── Shows: Questions transcend possible experience

GOD (Theology)
├── Traditional proofs fail
├── Ontological: Existence not a predicate
├── Cosmological: Misuse of causality
├── Teleological: At best shows designer, not God
└── But: God as regulative idea, postulate of practical reason

Key Vocabulary

Integration with Repository

Related Thinkers

• Cross-reference with thinker profiles if available

Related Themes

• thoughts/knowledge/: Epistemology, skepticism
• thoughts/consciousness/: Mind-body problem
• thoughts/existence/: Substance metaphysics

Reference Files

• methods.md: Methodical doubt, empirical analysis, transcendental method
• vocabulary.md: Technical terms glossary
• figures.md: Major philosophers with key works
• debates.md: Central controversies
• sources.md: Primary texts and scholarship