Philosophers Overview

Plato Principle Doctrines

Philosophy begins with dissatisfaction: the philosopher questions what “everyone knows.”

Distinction between Appearance and Reality: the senses show appearance; reason accesses truth.

Socrates as model philosopher: follows the Delphic oracle, exposes false wisdom, seeks virtue over reputation.

Wisdom = recognition of one’s own ignorance (Apology).

Plato Arguments

Elenchus (Socratic method) shows people contradict themselves and lack genuine knowledge.

“Divine mission”: Oracle says no one is wiser → Socrates interprets as a duty to test claims to knowledge.

Death is not to be feared because we don’t know it; injustice is worse than death.

Plato Objections

“Socratic Problem”: Plato’s depiction may be idealized.

Distrust of senses is contested—empirical knowledge is useful.

Plato Responses

Philosophy requires stepping back from common opinion.

Rational inquiry reveals stable truths that the senses alone cannot.

Descartes Principle Doctrines

Method of Doubt: reject anything that can be doubted to find certainty.

Forms of skepticism: sensory error, dreaming, evil demon hypothesis.

Cogito: “I think, therefore I am” → indubitable foundation; self is a thinking substance.

Dualism: mind = res cogitans (thinking); body = res extensa (extended).

Proofs of God: Causal Argument (idea of perfection requires perfect cause) and Ontological Argument.

Clear and Distinct Ideas guaranteed by a non-deceptive God.

Descartes Arguments

You can doubt everything except the fact you are thinking.

Mind and body have different essential properties → real distinction.

Only a perfect God could give us the idea of perfection.

Descartes Objections

Cartesian Circle (circular justification).

Mind–body interaction problem (Princess Elizabeth).

Excessive skepticism.

Descartes Responses

Clear and distinct ideas are self-validating while perceived.

Interaction is a basic fact of nature (pineal gland explanation).

Radical doubt is a method, not a permanent stance.

Hume Principle Doctrines

Empiricism: all ideas derive from impressions (Copy Thesis).

Distinction between Relations of Ideas (a priori, necessary) and Matters of Fact (a posteriori, contingent).

Causation: not perceived; only constant conjunction + habit.

Problem of Induction: cannot rationally justify that the future will resemble the past; no foundation for PUN (Principle of Uniformity of Nature).

Bundle Theory: the self is just a collection of perceptions connected by resemblance, causation, contiguity.

Hume Arguments

No experience ever reveals necessary connection.

Induction cannot be justified without circularity.

No impression of a “self,” therefore no idea of a substantial self.

Hume Objections

Undermines science

Cannot explain personal identity

Hume Responses

Habit/custom explains belief; humans naturally infer cause.

Identity is a “fiction” but a useful and inevitable one.

Kant Principle Doctrines

Analytic vs. Synthetic; A Priori vs. A Posteriori.

Synthetic a priori judgments: necessary for mathematics and science (e.g., causation).

Transcendental Idealism:

• Phenomena = appearances structured by our cognitive faculties.

• Noumena = things-in-themselves, unknowable.

Copernican Revolution: objects conform to our mode of cognition.

Limits of reason: must “annul knowledge to make room for faith.”

Kant Arguments

Against Hume: causation is a category of understanding, not derived from habit.

Space and time are a priori forms of intuition.

Noumenon required as boundary concept.

Kant Objections

Noumenal realm is unintelligible.

Makes reality overly mind-dependent.

Kant Responses

Noumena are not objects of knowledge, only limits.

Mind-structured experience makes science possible.

Hegel Principle Doctrines

Critique of Kant’s “natural supposition”: cannot test reason without using reason.

Knowledge develops dialectically through stages (“shapes of consciousness”).

Rejection of “things-in-themselves” as empty abstractions.

“The real is rational and the rational is real.”

Truth unfolds historically in the development of Spirit (Geist)

Hegel Arguments

Consciousness cannot step outside itself to check accuracy.

Understanding anything requires placing it in the whole.

Dialectic (Being → Nothing → Becoming) captures structure of reality.

Hegel Objections

System seems overly abstract or metaphysical.

Too optimistic about rationality in history

Hegel Responses

Philosophy must reflect the movement of reality, not static categories.

Kant’s noumena is worse (unknowable, empty) — Hegel offers a positive account.

Kierkegaard Principle Doctrines

Truth is Subjectivity: what matters is the individual’s inward relation to truth.

Objectivity cannot give access to God; “God is a subject.”

Faith = passionate inward commitment in the face of objective uncertainty.

Stages of life: Aesthetic → Ethical → Religious.

Critique of Hegel: system overlooks the existing individual.

Kierkegaard Arguments

Subjective reflection concerns how I exist, not detached truth.

Faith requires risk — cannot be grounded in objective certainty.

Kierkegaard Objections

Appears to promote irrationality.

Makes belief arbitrary.

Kierkegaard Responses

Faith is non-rational, not irrational.

One cannot avoid subjective commitment; life demands choices.

Nietzsche Principle Doctrines

Pessimism as Decadence: negative judgments of life arise from physiological and cultural decline.

Socrates as Symptom: over-reliance on reason/dialectic signals Greek degeneration.

Egyptianism: philosophers crave permanence and denigrate the senses; overvalue reason.

“True World” Doctrine: Western metaphysics invented a separate world of timeless truth (Plato → Christianity → Kant).

Historical death of the True World → it becomes a fiction.

If the True World dies, the “apparent world” also collapses — leaving only the world as interpreted, not as “mere appearance.”

Perspectivism: all knowledge is interpretive.

Nietzsche Arguments

Moral and metaphysical systems arise from weakness, not truth.

Philosophers reject the senses because the senses reveal becoming, flux, and life.

The “true world” loses function → becomes a useless relic.

Nietzsche Objections

Seems to deny objectivity.

Could lead to nihilism.

Nietzsche Responses

Not relativism: perspectives can be stronger or weaker.

“Death of God” opens space for revaluation of values (Übermensch).