modern-rationalism-empiricism

The Epistemological Turn

Medieval Philosophy: What is real? (Metaphysics first)

Modern Philosophy: What can we know? (Epistemology first)

Historical Context

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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

```

---

Core Commitments

| Thesis | Description |

|--------|-------------|

| Innate Ideas | Some ideas are in the mind prior to experience |

| Reason as Source | Reason, not sense, provides genuine knowledge |

| Mathematical Model | Philosophy should emulate mathematical certainty |

| Substance Metaphysics | Reality consists of substances with attributes |

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:

| Meditation | Content |

|------------|---------|

| I | Method of doubt |

| II | Cogito; nature of mind |

| III | Proofs of God's existence |

| IV | Truth and error |

| V | Essence of material things; ontological argument |

| VI | Real distinction of mind and body; external world |

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)

---

Core Commitments

| Thesis | Description |

|--------|-------------|

| No Innate Ideas | Mind begins as blank slate (tabula rasa) |

| Experience as Source | All knowledge derives from experience |

| Limits of Knowledge | We cannot know beyond experience |

| Analysis of Ideas | Break complex ideas into simple components |

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:

| Primary | Secondary |

|---------|-----------|

| In objects themselves | In perceiver |

| Extension, motion, number | Color, taste, sound |

| Resemble ideas | Don't resemble |

| Measurable | Subjective |

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)

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

1. Material substance is supposed to cause ideas

1. But we have no idea of material substance!

└── Abstract idea of "matter" is incoherent

1. Therefore, "material substance" is meaningless

1. Objects = collections of ideas

1. 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?

---

The Critical Project

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

Solution: Transcendental idealism

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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

```

---

| Term | Philosopher | Meaning |

|------|-------------|---------|

| Cogito | Descartes | "I think" — first certainty |

| Res cogitans | Descartes | Thinking substance (mind) |

| Res extensa | Descartes | Extended substance (body) |

| Clear and distinct | Descartes | Criterion of truth |

| Substance | Spinoza | That which is in itself |

| Attribute | Spinoza | What constitutes substance |

| Mode | Spinoza | Modification of substance |

| Monad | Leibniz | Simple substance |

| Pre-established harmony | Leibniz | God's synchronization |

| Tabula rasa | Locke | Blank slate |

| Primary qualities | Locke | In objects (extension) |

| Secondary qualities | Locke | In perceiver (color) |

| Esse est percipi | Berkeley | To be is to be perceived |

| Impressions | Hume | Vivid, original perceptions |

| Ideas | Hume | Faint copies of impressions |

| Phenomenon | Kant | Appearance, object of experience |

| Noumenon | Kant | Thing-in-itself, beyond experience |

| Transcendental | Kant | Concerning conditions of experience |

| Category | Kant | Pure concept of understanding |

| Synthetic a priori | Kant | Necessary truths about experience |

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Related Thinkers

• Cross-reference with thinker profiles if available

Related Themes

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

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• 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