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Human reason is the most reliable source of knowledge.

Attempts to provide rational foundation for the new science of Galileo and Newton

Emphasis on metaphysics, mathematics, and deductive reasoning: human reason seeing through appearances to underlying reality · Rationalist positions on the mind-body problem:

Dualism (Descartes): Mind and body are two distinct substances Materialism (Hobbes): Only matter is real Parallelism (Leibniz): Mind and body are separate but move in pre-established harmony like two stopwatches started at the same instant · René Descartes (1596–1650): Meditations on First Philosophy

Methodological doubt: Systematically doubts testimony of senses, reason § Influential foundation of skepticism in epistemology

Only certainty is “I think, therefore I am”; it would be impossible to think if one didn’t exist, so thought implies existence Sum res cogitans (“I am a thinking thing”): we are essentially minds, not bodies

Distinguishes three kinds of substance: § Matter: primary attribute is extension in space § Spirit (or Mind): primary attribute is thought § God: “infinite substance” whose primary attribute is existence ·

Baruch Spinoza (1632–1677): Strict rationalist; argued that there is only one substance (monism) and that it is both God and the universe(pantheism) ·

Gottfried Wilhelm Leibniz (1646–1716)

Pioneer in math and logic: invents calculus (as does Newton)

Possible worlds: A fact is necessary if it is true in all possible worlds,contingent if it is false in some possible worlds, and impossible if it is false in all possible worlds § “Principle of the best”: Ours is the “best of all possible worlds”; ridiculed by Voltaire’s Candide through the figure of Pangloss Reality is made up of monads, simple, non-extended, unchanging substances that are the building blocks of the universe

Empiricism · All knowledge comes from experience

Rejects the rationalists’ emphasis on metaphysical speculation and innate knowledge

Emphasis on epistemology, scientific experimentation, and observation · John Locke (1632–1704): Essay Concerning Human Understanding

Tabula rasa: The mind is a blank slate at birth; all understanding comes from experience and reflection upon that experience.

Role of philosopher is as “underlabourer” to natural sciences; clear up language to secure a solid foundation for science · George Berkeley (1685–1753)

Idealism: Things have no material existence, but exist only as ideas, which minds perceive and experience (esse est percipi: “being is being perceived”) Things exist independent of individual perception only because God perceives everything · David Hume (1711–1776): Treatise of Human Nature

Hume’s fork: All knowledge is either a relation of ideas (independent of experience, e.g., math) or a matter of fact (based on experience, e.g., science). Causality and uniformity in nature are not rationally justified ; they are simply the result of custom and habit.

The Enlightenment

Enlightenment is an 18th-century movement that seeks to better society through the use of reason and philosophy · Philosophes: 18th-century French philosophers such as Denis Diderot, Voltaire, Baron de Montesquieu

Reason combats ignorance and betters the human condition. · Deism: Belief that God created a universe governed by set principles that can be discerned with science and reason (Voltaire) God is a “blind watchmaker”: no divine intervention

Immanuel Kant (1724-1804) · Metaphysics/epistemology: Critique of Pure Reason

Transcendental idealism synthesizes rationalism and empiricism Distinguishes between: § Analytic propositions: Predicate concept is contained in subject concept (e.g., all unmarried men are bachelors) § Synthetic propositions: Predicate concept is not contained in subject concept (e.g., all swans are white)

And between: § A priori knowledge: Knowledge from reason § A posteriori knowledge: Knowledge from experience Space, time, and causality are synthetic a priori concepts of the understanding: reality is shaped by the perceiving mind

Human knowledge is limited to phenomena (reality as presented to the mind) Noumena or things-in-themselves exist, but are unknowable § Metaphysics must be limited to a critique of human reason · Ethics: Grounding for the Metaphysics of Morals Ethics based in human autonomy: capacity for rational deliberation

Categorical imperative: Act only in such a way that you could want the motivating principle of your action to become a universal law.

German Idealism (and Its Critics) ·

Influenced by Kant but rejects his view of the unknowable noumenal world;the only real world is the rational world, which is knowablen · Important early idealists include Fichte and Schelling · G. W. F. Hegel (1770–1831)

All of reality is part of an interconnected system that undergoes a logical historical development § The Absolute Idea is the final expression of the system.

The system functions through the dialectic: the development of ideas through a back-and-forth interaction with opposing ideas § Thesis (an initial argument) and antithesis (the opposite argument) combine to form a synthesis

Hegel’s theory of history § Based on the idea of the dialectical development of spirit in history § The Absolute Spirit is the final end of this process; mirrors Absolute Idea § Zeitgeist: The spirit of a particular age · Arthur Schopenhauer (1788–1860): Fierce opponent of Hegelian idealism

Divides the world into will (things-in-themselves) and representation(phenomena) · Other critics of Hegel include Marx And Kierkegaard

Marxism · Karl Marx (1818–1883)

Rejects an individualistic state of nature; human life is necessarily social § Human nature is an expression of labor, or human activity, performed for the benefit of society § Alienation: Workers forced to sell their labor for a wage are detached from their labor, and hence from their human nature

Dialectical Materialism: Marx’s theory of history

Expresses Hegel’s historicism in material rather than spiritual terms § History is embodied in changing relationships of production (economics) § Dialectic of class struggle moves through feudalism and capitalism towardcommunism: workers collectively own the means of production

Ideology: Ideas that express the interest of a particular social class, such as the bourgeoisie · 20th-century Marxism

Social rights: Rights based on humans’ nature as social beings. Includes rights to food and shelter Antonio Gramsci (1891–1937): Discusses hegemony, the power of the ruling class to create consent for its position through the use of social and cultural forces.

Frankfurt School (founded 1923): Includes Max Horkheimer, Theodor W. Adorno, Herbert Marcuse, Walter Benjamin, and Jürgen Habermas § Critical theory: Aims to change society by understanding ideas as products of social processes; rejects determinism


Existentialism stems from the belief that ethics and meaning must come from an individual experience of the world. · Søren Kierkegaard (1813–1855)

Rejects Hegelian system; focuses on truth as subjective meaning Three “stages on life’s way”: § Aesthetic: individualistic emphasis on physical sensations § Ethical: selfless emphasis on public good § Religious: individual’s personal relationship with God

Anxiety (angst): the fear one feels in face of one’s own freedom Leap of faith: Religion cannot be understood rationally, but requires a personal choice to believe in God · Friedrich Nietzsche (1844–1900)

Opposes nihilism, a belief in nothing § ”God is dead”: Christian faith is no longer a generally accepted basis for morality; with the rise of atheism, Western culture is decentered and has no positive values Will to power: The fundamental drive motivating all things in the universe § Represents an “instinct for freedom” or drive for autonomy from and dominance over all other wills

Perspectivism: There is no absolute truth, merely different perspectives Superman (or “overman”): someone who has so refined his will to power that he has freed himself from all outside influences and created his own values (described in Thus Spoke Zarathustra) · Phenomenology: A theory of knowledge focused on the examination of an individual’s mental processes

Intentionality: The act of thinking involves thinking about something. “The direction of the mind on an object.” (Franz Brentano, 1838–1917)

Bracketing: Setting aside assumptions and theoretical speculations about the world; allows objective investigation of mental functions and intentionality.

Edmund Husserl (1859–1938): Consciousness, free from assumptions, is the essence of experience. · Martin Heidegger (1889–1976): Focuses on the problem of actually “being” (in German, dasein) rather than reflecting on consciousness ·

Jean-Paul Sartre (1905–1980): Being and Nothingness: “Existence precedes essence”; there is no essential “human nature.” We define who we are by the choices we make.

Simone de Beauvoir (1908–1986): The Second Sex: Patriarchal society objectifies women, inhibiting subjective experience

American Philosophy

Transcendentalism: Emphasizes democratic spirituality, intuitive knowledge, and direct connection between people, God, and nature

Ralph Waldo Emerson (1803–1882): Emphasizes self-reliance and personal freedom.

Henry David Thoreau (1817–1862): Rejects dehumanizing materialism in favor of spiritual communion with nature ·

Pragmatism: Knowledge is a guide for action, not a search for abstract truth.

C. S. Peirce (1839–1914): The meaning of an idea consists of the consequences to which it would lead William James (1842–1910): To fully understand something we must understand all of its consequences; true beliefs will lead to positive consequences

Analytic Philosophy

Applies advances in math and logic to clarifying philosophical method

“Linguistic turn” in philosophy: solves philosophical problems by analyzing the language in which they’re expressed.

Hostile to metaphysics: meaningful questions should be settled through logic and scientific investigation alone · Gottlob Frege (1848–1925)

Develops quantifier logic, first major advance in logic since Aristotle

Uses logic to analyze meaning: § Sense: What a person knows when they understand a word § Reference: Object to which the word refers·

Bertrand Russell (1872–1970)

Logicism: Attempts to reconstruct math from logical axioms ( Principia Mathematica, written with A. N. Whitehead)

Russell’s Paradox: Does a class exist that consists of all classes that are not members of themselves? § There is no noncontradictory answer to this question: serious problem for logic

Grammar masks meaning: logical analysis of sentences brings out underlying logical form Logical empricism: All knowledge is built from unanalyzable sense data.

Ludwig Wittgenstein (1889–1951): Philosophical problems dissolve when we understand the language in which they’re expressed.

Tractatus Logico-Philosophicus (1921): Only scientific propositions have meaning; propositions about ethics, metaphysics, etc. are meaningless.

Philosophical Investigations (1953): Ordinary language philosophy:Meanings of words lie in their everyday use. ·

Logical positivism (the Vienna Circle: Schlick, Carnap, Neurath) Verification principle: The meaning of a sentence is its means of verification; unverifiable sentences (e.g., metaphysics) are meaningless ·

Kurt Gödel (1906–1978): Incompleteness Theorem: All logical systems necessarily contain statements that cannot be proved within the system itself · W. V. O. Quine (1908–2000): Naturalized epistemology Criticizes analytic/synthetic distinction: Any statement in a system can be true, given enough adjustment of other statements in the system


Ferdinand de Saussure (1857–1913): Semiology: Language is a structured system of signs

Distinguishes between: § Signified: The thing to which a word refers § Signifier: The word that does the referring. The relationship between signifier and signified is arbitrary: words only have meaning in relation to other words.

Similarly separates: § Langue: The general system and rules of language § Parole: Concrete utterances whose meaning comes only from their relationship to other words in the system · Other structuralists apply semiology to anthropology (Lévi-Strauss), psychology (Lacan), and myth (Barthes) ·


Meaning is fluid; there is no absolute truth.

Michel Foucault (1926–1984): What is accepted as knowledge reflects not reality but the structures of power present in a particular historical period.

Jacques Derrida (1930–2004): Deconstruction: Method of taking apart, or invalidating, the presumed meaning of a text · Feminist epistemology: The human experience is more than just the male experience. Subjectivity: Emphasizes the validity of the views or feelings of a particular subject Scientific and philosophical “objectivity” can be seen as forms of malesubjectivity.