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An algorithm by means of which to establish, in a finite number of steps, whether a statement form is tautologous or whether an argument form is valid. Drawing Venn diagrams provides a decision procedure for a modern interpretation of categorical logic, and truth-tables give a decision procedure for the propositional calculus, but there is no decision procedure for quantification theory.
Also see EB.
Interpretive method that denies the priority or privilege of any single reading of a text (even if guided by the intentions of its author) and tries to show that the text is incoherent because its own key terms can be understood only in relation to their suppressed opposites. Deconstructionists like Derrida seek to uncover the internal conflicts that tend to undermine (or at least to "decenter") the putative significance of any text. In ordinary language, for example, someone who says, "If I may be perfectly candid for a moment, . . ." thereby betrays a reluctanceat least in the past and, probably, even in the present caseto do so, and this difference points toward a systematic ambiguity in the very notions of honesty and truth.
Recommended Reading: Deconstruction in a Nutshell: A Conversation With Jacques Derrida, ed. by John D. Caputo (Fordham, 1997); Christopher Norris, Deconstruction and the Unfinished Project of Modernity (Routledge, 2000); Deconstruction in Context: Literature and Philosophy, ed. by Mark C. Taylor (Chicago, 1986); and Penelope Deutscher, Yielding Gender: Feminism, Deconstruction, and the History of Philosophy (Routledge, 1997).
German mathematician who showed that every real number can be defined by reference to a 'cut' or division between sets of rational numbers. Dedekind also identified as axiomatic foundations of arithmetic what later became known as the Peano postulates.
Recommended Reading: Richard Dedekind, Essays on the Theory of Numbers, tr. by Wooster W. Beman (Dover, 1963) and Richard Dedekind, Theory of Algebraic Integers, tr. by John Stillwell (Cambridge, 1996).
Someone who does not know that the morning star is the planet Venus, for example, could believe the truth, de dicto, of the proposition, "The morning star is larger than Venus," even though no one would believe de re that Venus is larger than itself.
Recommended Reading: Alvin Plantinga, The Nature of Necessity (Clarendon, 1989) and Saul A. Kripke, Naming and Necessity (Harvard, 1980).
Distinction in logic between types of reasoning, arguments, or inferences. In a deductive argument, the truth of the premises is supposed to guarantee the truth of the conclusion; in an inductive argument, the truth of the premises merely makes it probable that the conclusion is true.
Recommended Reading: Patrick Suppes, Introduction to Logic (Dover, 1999) and Richard L. Wilson, Logic: Deductive, Inductive and Informal Reasoning (Kendall/Hunt, 1993).
Distinction between the grounds for a condition that merely happens to obtain (de facto) and one that holds as a matter of right or law (de jure). The maximum speed at which an automobile may lawfully travel on the highway is 70 m.p.h. de jure, but the de facto speed limit on a busy afternoon is only about 50 m.p.h.
An expression that claims to refer to the single being that possesses some unique feature. Russell showed nearly a century ago that the proper analysis of such expressions, as the joint assertion of several distinct propositions, resolves a number of otherwise troubling difficulties.
Recommended Reading: Definite Descriptions: A Reader, ed. by Gary Ostertag (Bradford, 1998); Stephen Neale, Descriptions (Bradford, 1993); and Jaakko Hintikka and Jack Kulas, Anaphora and Definite Descriptions: Two Applications of Game-Theoretical Semantics (Kluwer, 1985).
Recommended Reading: Essays on Definition, ed. by Juan C. Sager (Benjamins, 2000); Richard Robinson, Definition (Clarendon, 1950); and Definitions and Definability: Philosophical Perspectives, ed. by James H. Fetzer, David Shatz, and George N. Schlesinger (Kluwer, 1991).
Belief in god based entirely on reason, without any reference to faith, revelation, or institutional religion. During the seventeenth and eighteenth centuries, advances in the natural sciences often fostered confidence that the regularity of nature reflects the benevolence of a divine providence. This confidence, together with a widespread distrust of the church, made deism a popular view in England and on the continent. Thus, in distinct ways, Toland, Lord Herbert, Paine, Rousseau, and Voltaire were all deists.
Recommended Reading: John Toland's Christianity Not Mysterious: Text, Associated Works and Critical Essays, ed. by Alan Harrison, Richard Kearney, and Philip McGuinness (Dufour, 1997); Thomas Paine, Age of Reason (Lyle Stuart, 1989); William Stephens, An Account of the Growth of Deism in England (AMS, 1995); and The Radical Rhetoric of the English Deists: The Discourse of Skepticism, 1680-1750, ed. by James A. Herrick and Thomas W. Benson (South Carolina, 1997).
As a matter of law, not merely as a matter of fact. See de facto / de jure.
French philosopher who used critical interpretations of Spinoza [Spinoza et le problème de l'expression (Expressionism in Philosophy: Spinoza) (1968)] and Nietzsche [Nietzsche et la philosophie (Nietzsche and Philosophy) (1962)] as the basis for a profound attack on modernist rationality. Like Foucault, Deleuze was sharply critical of the neo-Freudian psychoanalytic theories of Jacques Lacan. In collaboration with psychoanalyst Félix Guattari, Deleuze published L'Anti-Oedipe (Anti-Oedipus: Capitalism and Schizophrenia) (1972), an extended critique of contemporary political structures, and Qu'est-ce que la philosophie? (What is Philosophy?) (1981). Deleuze developed his own theories of meaning and interpretation in Différence et répétition (Difference and Repetition) (1968) and Logique du sens (The Logic of Sense) (1969).
Recommended Reading: Deleuze: A Critical Reader, ed. by Paul Patton (Blackwell, 1996); Dorothea Olkowski, Gilles Deleuze and the Ruin of Representation (California, 1999); Todd May, Reconsidering Difference: Nancy, Derrida, Levinas, and Deleuze (Penn. State, 1997); Claire Colebrook, Gilles Deleuze (Routledge, 1997); Gillian Howie, Deleuze and Spinoza: An Aura of Expressionism (Palgrave, 2002); Paul Patton, Deleuze and the Political (Routledge, 2000); Tamsin E. Lorraine, Irigaray & Deleuze: Experiments in Visceral Philosophy (Cornell, 1999); and John Rajchman, The Deleuze Connections (MIT, 2000).
Presocratic Greek philosopher. As the originator of classical atomism, Democritus maintained in opposition to the Eleatics that the universe comprises a plurality of distinct entities that really do move. The haphazard collisions of these individually indestructible atoms, he believed, account for the formation and dissolution of all observable things. Long before its appropriation by Epicurus, this doctrine produced an attitude toward human life that earned Democritus a reputation as "the laughing philosopher."
Recommended Reading: Paul Cartledge, Democritus (Routledge, 1999) and C. C. W. Taylor, The Atomists: Leucippus and Democritus (Toronto, 1999).
British mathematician who recognized the need to expand the notion of logical validity beyond the narrow confines of Aristotelian syllogistic. His works include Essay on Probabilities (1838), Formal Logic (1847), and Budget of Paradoxes (1872). De Morgan developed the standard statement of De Morgan's Theorems, a pair of logical relationships earlier noted by Ockham and Geulincx.
Recommended Reading: Robert Adamson, Short History of Logic (Irvington, 1961) and Daniel Davy Merrill, Augustus De Morgan and the Logic of Relations (Kluwer, 1991).
A rule of replacement of the forms:
~ ( p • q ) ≡ ( ~ p ∨ ~ q ) ~ ( p ∨ q ) ≡ ( ~ p • ~ q )
Example: "It is not the case that I am both bald and fat" is equivalent to "Either I am not bald or I am not fat."
Truth-table analysis demonstrates the reliability of these logical relationships, as does a set-theoretical proof.
American philosopher; author of Brainstorms (1978), The Intentional Stance (1987), and Consciousness Explained (1991); Co-editor (with Douglas Hofstadter) of The Mind's I (1981). Dennett's careful application of neuroscientific research to the philosophy of mind is characterized by the frequent use of ingenious thought-experiments. Many of Dennett's papers are available on-line at the Center for Cognitive Studies.
Recommended Reading: Daniel C. Dennett, Elbow Room (MIT, 1984); Daniel C. Dennett, Darwin's Dangerous Idea: Evolution and the Meanings of Life (Touchstone, 1996); Daniel C. Dennett, Brainchildren: Essays on Designing Minds, 1984-1996 (Bradford, 1998); Daniel Dennett, ed. by Andrew Brook and Don Ross (Cambridge, 2002); Dennett and His Critics: Demystifying Mind, ed. by Bo Dahlbom (Blackwell, 1995); and Dennett's Philosophy: A Comprehensive Assessment, ed. by Don Ross, Andrew Brook, and David Thompson (MIT, 2000).
Mill's distinction between the things to which a term refers (its denotation) and the meaning of the term (its connotation). In modern logic, this distinction is often assimilated to the distinction between the extension and intension of an expression.
Recommended Reading: Ermanno Bencivenga, Logic, Bivalence, and Denotation (Ridgeview, 1991).
A formal fallacy of the form:
p ⊃ q ~ p _______ ~ q
Example: "If Rover is a cat, then Rover is a mammal. But Rover is not a cat. So, Rover is not a mammal."
Notice the crucial difference between this pattern of reasoning and the valid Modus Tollens.
A deontological normative theory holds that moral worth is an intrinsic feature of human actions, determined by formal rules of conduct. Thus, deontologists like Kant suppose that moral obligation rests solely upon duty, without requiring any reference to the practical consequences that dutiful actions may happen have.
Recommended Reading: Immanuel Kant, Grounding for the Metaphysics of Morals, tr. by James W. Ellington (Hackett, 1993); Roger J. Sullivan, An Introduction to Kant's Ethics (Cambridge, 1994); and Philip Stratton-Lake, Kant, Duty, and Moral Worth (Routledge, 2001).