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Ramsey, Frank Plumpton (1903-1930)

British mathematician and philosopher who contributed to the second edition of Russell and Whitehead's Principia Mathematica. Ramsey's "Truth and Probability" (1926) and Foundations of Mathematics (1931) clarified the nature of semantic paradox, developed modern applications of the probability calculus, and introduced the redundancy theory of truth. He was an early admirer of Wittgenstein,whose Tractatus Ramsey translated into English and whose return to England in 1929 he helped to arrange.

Recommended Reading: Frank Plumpton Ramsey, Philosophical Papers, ed. by D. H. Mellor (Cambridge, 1990) and Nils-Eric Sahlin, The Philosophy of F. P. Ramsey (Cambridge, 1990).

Also see MMT.

Ramus, Petrus (Pierre de la Ramée) (1515-1572)

French logician. In his Dialecticae Partitiones (The Structure of Dialectic) (1543), Ramus attacked the influence of Aristotelean thinking on education and philosophy, proposing an alternative method of reasoning that emphasized the invention of rhetorical dichotomies. This work was a significant influence on that of Bacon and Hobbes.

Recommended Reading: Arguments in Rhetoric Against Quintilian: Translation and Text of Peter Ramus's Rhetoricae Distinctiones in Quintilianum, tr. by James Murphy and Carole Newlands (Northern Illinois, 1986).

Also see SEP, EB, and ELC.

Rand, Ayn (Alissa Rosenbaum) (1905-1982)

Russian-American novelist and essayist. In addition to the social theories reflected in her popular novels, The Fountainhead (1943), Anthem (1946), and Atlas Shrugged (1947). Rand introduced the philosophy of objectivism in Introduction to Objectivist Epistemology (1966) and defended a version of ethical egoism in The Virtue of Selfishness: A New Concept of Egoism (1964).

Recommended Reading: The Ayn Rand Reader, ed. by Gary Hull and Leonard Peikoff (Plume, 1999) Chris Matthew Sciabarra, Ayn Rand: Her Life and Thought (Objectivist Center, 1999); Tibor R. Machan, Ayn Rand (Peter Lang, 2000); David Kelley, The Contested Legacy of Ayn Rand (Objectivist Center, 2000); Leonard Peikoff, Objectivism: The Philosophy of Ayn Rand (Meridian, 1993); and Feminist Interpretations of Ayn Rand, ed. by Mimi Reisel Gladstein and Chris Matthew Sciabarra (Penn. State, 1999).

Also see SEP, The Ayn Rand Society, The Objectivist Center, EB, and ELC.


Reliance on reason {Lat. ratio} as the only reliable source of human knowledge. In the most general application, rationalism offers a naturalistic alternative to appeals to religious accounts of human nature and conduct.

More specifically, rationalism is the epistemological theory that significant knowledge of the world can best be achieved by a priori means; it therefore stands in contrast to empiricism. Prominent rationalists of the modern period include Descartes, Spinoza, and Leibniz.

Recommended Reading: The Rationalists (Anchor, 1960); The Rationalists: Critical Essays on Descartes, Spinoza, and Leibniz, ed. by Dirk Pereboom (Rowman & Littlefield, 1999); John Cottingham, Rationalism (St. Augustine Press, 1997); David Miller, Critical Rationalism: A Restatement and Defence (Open Court, 1994); and Laurence Bonjour, In Defense of Pure Reason: A Rationalist Account of A Priori Justification (Cambridge, 1997).

Also see SEP, IEP, EB, and ISM.

Rawls, John (1921-2002 )

American political philosopher. As presented in A Theory of Justice (1971), Rawls's concept of "justice as fairness" offers a non-historical or hypothetical variation on the social contract theory, in which rational agents make social decisions from behind a "veil of ignorance" that prevents them from knowing in advance what status they will hold. According to Rawls, this method will produce a society where individual liberties are maximized for all citizens and social inequality is justifiable only under conditions that would be beneficial for its least-favored members. Further exposition of this theory, along with a restatement Rawls's opposition to utilitarianism and an examination of political pluralism, appear in Political Liberalism (1993). Two Concepts of Rules (1955) is an early statement of Rawls's basic principles.

Recommended Reading: John Rawls, Collected Papers, ed. by Samuel Freeman (Harvard, 2001); John Rawls, The Law of Peoples (Harvard, 2001); Chandran Kukathas and Philip Pettit, Rawls: A Theory of Justice and Its Critics (Stanford, 1991); and Reading Rawls: Critical Studies on Rawls on Rawls 'A Theory of Justice', ed. by Norman Daniels (Stanford, 1989).

Also see IEP, SEP on Rawls and the original position, Robert Johnson, Mary Lyn Stoll, and EB.


Belief that universals exist independently of the particulars that instantiate them. Realists hold that each general term signifies a real feature or quality, which is numerically the same in all the things to which that term applies. Thus, opposed to nominalism.

Recommended Reading: The Problem of Universals, ed. by Andrew B. Schoedinger (Humanity, 1991); Richard I. Aaron, Our Knowledge of Universals (Haskell House, 1975); Theodore Scaltsas, Substances and Universals in Aristotle's Metaphysics (Cornell, 1994); Properties, ed. by D. H. Mellor and Alex Oliver (Oxford, 1997); and D. M. Armstrong, Universals: An Opinionated Introduction (Westview, 1989).

Also see SEP and EB.

realism, perceptual

Belief that material objects exist independently of our perception of them. (Thus, opposed to idealism.) Realistic theories of perception include both representationalism, in which awareness of objects is mediated by our ideas of them, and direct realism, which presumes an immediate relation between observer and observed.

Recommended Reading: Critical Realism: Essential Readings, ed. by Margaret Archer, Roy Bhaskar, Andrew Collier, and Tony Lawson (Routledge, 1999); David Kelley, The Evidence of the Senses: A Realist Theory of Perception (Louisiana State, 1988); Hilary Putnam, Realism With a Human Face (Harvard, 1992); Joseph Margolis, Selves and Other Texts: The Case for Cultural Realism (Penn State, 2001); Stathis Psillos, Scientific Realism: How Science Tracks Truth (Routledge, 1999); Gustav Bergmann, Realism: A Critique of Brentano & Meinong (Wisconsin, 1967); and Simon Blackburn, Essays in Quasi-Realism (Oxford, 1995).

Also see SEP on realism and scientific realism, ISM, and DPM.

reality {Ger. Wirklichkeit}

The totality of what is, as opposed to what merely seems to be. Metaphysicians and ontologists differ widely in their convictions about what kinds of entities are properly included.

Recommended Reading: Peter Loptson, Reality: Fundamental Topics in Metaphysics (Toronto, 2001); Milton K. Munitz, The Question of Reality (Princeton, 1992); John W. Yolton, Realism and Appearances: An Essay in Ontology (Cambridge, 2000); John R. Searle, The Construction of Social Reality (Free Press, 1997); and Robert Kirk, Relativism and Reality: A Contemporary Introduction (Routledge, 1999).

Also see Stephen Daniel.

reason {Ger. Vernunft}

The intellectual ability to apprehend the truth cognitively, either immediately in intuition, or by means of a process of inference.

Recommended Reading: Thomas Nagel, The Last Word (Oxford, 1996); Robert Audi, The Architecture of Reason: The Structure and Substance of Rationality (Oxford, 2001); Christopher McMahon, Collective Rationality and Collective Reasoning (Cambridge, 2001); Common Sense, Reasoning, and Rationality, ed. by Renée Elio (Oxford, 2002); Harold I. Brown, Rationality (Routledge, 1988); Reason and Nature: Essays in the Theory of Rationality, ed. by J.L. Bermúdez and Alan Millar (Oxford, 2002); Lynn Holt, Apprehension: Reason in the Absence of Rules (Ashgate, 2002); Martin Hollis, The Cunning of Reason (Cambridge, 1988); Max Horkheimer, Eclipse of Reason (Continuum, 1974); Ernest Gellner, Reason and Culture: The Historic Role of Rationality and Rationalism (Blackwell, 1992); and Paul M. Churchland, The Engine of Reason, the Seat of the Soul: A Philosophical Journey into the Brain (MIT, 1996).

Also see SEP on medieval theories of practical rationality and historicist theories of rationality, EB, and CE.

recollection {Gk. αναμνησις [anámnêsis]}

Belief that we come to know fundamental truths by recalling our acquaintance with their eternal objects before birth. Plato (perhaps following the lead of Socrates) defended recollection as the source of our knowledge of mathematics and morality in Meno, Phaedo, and The Republic.

Recommended Reading: Plato, Five Dialogues: Euthyphro, Apology, Crito, Meno, Phaedo, tr. by G.M.A. Grube (Hackett, 1983) and Dominic Scott, Recollection and Experience: Plato's Theory of Learning and Its Successors (Cambridge, 1995).


Capable of being indefinitely re-applied to the results of its own application. Hence, a recursive definition is one that begins with one or more initial instances and then specifies the repeatable rules for deriving others. Thus, for example:

"A person's descendants include that person's children and all of their descendants" is a recursive definition [not a circular definition] of the word "descendant".

Recommended Reading: Robert L. Causey, Logic, Sets, and Recursion (Jones & Bartlett, 2001); Raymond M. Smullyan, Recursion Theory for Metamathematics (Oxford, 1993); George S. Boolos and Richard D. Jeffrey, Computability and Logic (Cambridge, 1989); and Joseph R. Shoenfield, Recursion Theory (A. K. Peters, 2001).

The compound statements of the propositional calculus and the natural numbers of arithmetic are often defined recursively.

reductio ad absurdum

A method of proving that a proposition must be false [or true] by assuming the truth [or falsity] of the proposition and then showing that this assumption, taken together with other premises whose truth is already established, would lead to a contradiction (or, at least, to an obvious falsehood). This method is sometimes called indirect proof.

Also see EB.


Belief that statements or expressions of one sort can be replaced systematically by statements or expressions of a simpler or more certain kind. Thus, for example, some philosophers have held that arithmetic can be reduced to logic, that the mental can be reduced to the physical, or that the life sciences can be reduced to the physical sciences.

Recommended Reading: Ernest Nagel, Structure of Science (Hackett, 1979); Richard H. Jones, Reductionism: Analysis and the Fullness of Reality (Bucknell, 2000); Robert W. Batterman, The Devil in the Details: Asymptotic Reasoning in Explanation, Reduction and Emergence (Oxford, 2001); Reduction, Explanation, and Realism, ed. by David Charles and Kathleen Lennon (Oxford, 1993); Valerie Gray Hardcastle, How to Build a Theory in Cognitive Science (SUNY, 1996); and Harold Kincaid, Individualism and the Unity of Science (Rowman & Littlefield, 1997).

Also see ISM and EB.

redundancy theory of truth

Belief that it is always logically superfluous to claim that a proposition is true, since this claim adds nothing further to a simple affirmation of the proposition itself. "It is true that I am bald." means the same thing as "I am bald."

Recommended Reading: Theories of Truth, ed. by Paul Horwich (Dartmouth, 1994) and Richard L. Kirkham, Theories of Truth: A Critical Introduction (Bradford, 1995).

Also see SEP.

reference {Ger. Bedeutung}

The relation that holds between a term and the things to which it applies; see sense / reference.

Recommended Reading: A. W. Moore, Meaning and Reference (Oxford, 1993); The Varieties of Reference, ed. by Gareth Evans, Garbeth Evans, and John McDowell (Oxford, 1983); P. T. Geach, Reference and Generality: An Examination of Some Medieval and Modern Theories (Cornell, 1962); John Perry, Reference and Reflexivity (CSLI, 2001); The Frege Reader, ed. by Michael Beaney (Blackwell, 1997); and The New Theory of Reference - Kripke, Marcus, and Its Origins, ed. by Paul W. Humphreys and James H. Fetzer (Kluwer, 1999).

Also see SEP.

Regan, Tom (1938- )

American philosopher. In The Case for Animal Rights (1983) and The Thee Generation: Reflections on the Coming Revolution (1991) Regan develops a comprehensive theory in favor of granting moral respect to non-human animals.

Recommended Reading: Tom Regan, Defending Animal Rights (Illinois, 2001) and Carl Cohen and Tom Regan, The Animal Rights Debate (Rowman & Littlefield, 2001).

Also see IEP.

Régis, Pierre-Sylvain (1632-1707)

French Cartesian philosopher. Unable to secure an adequate metaphysical defense of mind-body dualism, Regis proposed that the interaction of accidentally conjoined substances can only be accepted on faith.

Reichenbach, Hans (1891-1953)

German-American philosopher of science whose Philosophie der Raum-Zeit-Lehre (The Philosophy of Space and Time) (1928) considered the philosophical implications of Einstein's theory of relativity. Reichenbach contributed significantly to the mathematical conception of probability as relative frequency of occurrence. Despite his long association with the logical positivists, in Experience and Prediction (1938), he explicitly rejected their reductionist and phenomenalist aims. The Rise of Scientific Philosophy (1951) provides an accessible summary of Reichenbach's thought.

Recommended Reading: Hans Reichenbach, Philosophic Foundations of Quantum Mechanics (Dover, 1998); Hans Reichenbach,The Direction of Time (Dover, 2000); Karin Gerner, Hans Reichenbach: sein Leben und Wirken: eine wissenschaftliche Biographie; and Logical Empiricism and the Special Sciences: Reichenbach, Feigl, and Nagel, ed. by Sahotra Sarkar (Garland, 1996).

Also see IEP, SEP, EB, and ELC.

Reid, Thomas (1710-1796)

Scottish philosopher who developed "common-sense" philosophy in reaction against the skepticism of Hume in his An Inquiry into the Human Mind on the Principles of Common Sense (1764). Reid criticized the trend of modern philosophy in Essays on the Intellectual Powers (1785), rejecting the representationalism he called "the way of ideas" in order to defend direct realism in perception. In Essays on the Active Powers of the Human Mind (1788) Reid developed an intuitionist moral theory that drew heavily upon the natural law tradition.

Recommended Reading: Thomas Reid's Inquiry and Essays (Hackett, 1983); The Correspondence of Thomas Reid, ed. by Paul Wood (Edinburgh, 2002); Keith Lehrer, Thomas Reid (Routledge, 1999); Peimin Ni, On Reid (Wadsworth, 2000); Philip de Bary, Thomas Reid and Scepticism: His Reliabilist Response (Routledge, 2002); Nicholas Wolterstorff, Thomas Reid and the Story of Epistemology (Cambridge, 2001); The Philosophy of Thomas Reid, ed. by Melvin Dalgarno and Eric Matthews (Kluwer, 1989); and William L. Rowe, Thomas Reid on Freedom and Morality (Cornell, 1991).

Also see SEP on Reid, his ethics, and memory and identity, ELC, and EB.


Improperly treating something as if it were an object. In the political thought of Lukacs and other Marxists, reification often involves trying to turn human beings into marketable commodities. The philosophical reification of abstract concepts is commonly called hypostasization.

Recommended Reading: Joseph Gabel, False Consciousness: An Essay on Reification (Harpercollins, 1985) and Bryan D. Palmer, Descent into Discourse: The Reification of Language and the Writing of Social History (Temple, 1990).


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