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Nagel, Ernest (1901-1985)
Ernest Nagel

American philosopher of science who improved understanding of scientific explanation in his Introduction to Logic and Scientific Method (1934) and Principles of the Theory of Probability (1939). Nagel combined the pragmatic method of Peirce with the logical positivism of the Vienna Circle. His The Structure of Science (1961) argues on behalf of the systematic reduction to physical science of social and behavioral sciences, despite their apparent reference to non-observable entities and appeal to judgments of value.

Recommended Reading: Ernest Nagel and James R. Newman, Gödel's Proof (NYU, 1983); Ernest Nagel, Teleology Revisited (Columbia, 1982); and Logical Empiricism and the Special Sciences: Reichenbach, Feigl, and Nagel, ed. by Sahotra Sarkar (Garland, 1996).

Also see EB.

Nagel, Thomas (1937- )

American philosopher; author of The Possibility of Altruism (1970), "Brain Bisection and the Unity of Consciousness" (1971) and "What Is It Like to Be a Bat?" (1974). In The View from Nowhere (1989) Nagel tries to reconcile the subjective and personal elements of human life with the urge to achieve objective and impersonal truths about life and value. On-line papers by Nagel include "Justice and Nature" (1996), "Conceiving the Impossible and the Mind-Body Problem" (1998), and "Concealment and Exposure" (1998).

Recommended Reading: Thomas Nagel, What Does It All Mean: A Very Short Introduction to Philosophy (Oxford, 1987); Thomas Nagel, Mortal Questions (Cambridge, 1991); Thomas Nagel, The Last Word (Oxford, 1996); Thomas Nagel, Other Minds: Critical Essays 1969-1994 (Oxford, 1999); Thomas Nagel, Equality and Partiality (Oxford, 2001); and Thomas Nagel, Concealment and Exposure and Other Essays (Oxford, 2002).

Also see IEP.

natural law theory

Belief that the principles of human conduct can be derived from a proper understanding of human nature in the context of the universe as a rational whole. Although voluntarists suppose that god could will anything at all, Aquinas held that even the divine will is conditioned by reason. Thus, the natural law provides a non-revelatory basis for all human social conduct. Modern appeals to natural law are the foundation for social thought in Grotius and Pufendorf.

Recommended Reading: John Finnis, Aquinas: Moral, Political, and Legal Theory (Oxford, 1998); Samuel Pufendorf, On the Duty of Man and Citizen According to Natural Law, ed. by James Tully and Michael Silverthorne (Cambridge, 1991); Joel Feinberg, Problems at the Root of Law (Oxford, 2002); Mark Murphy, Natural Law and Practical Rationality (Cambridge, 2001); Martin Rhonheimer, Natural Law and Practical Reason: A Thomist View of Moral Autonomy, tr. by Gerald Malsbary (Fordham, 2000); and Robert P. George, In Defense of Natural Law (Oxford, 2001).

Also see SEP on natural law theories and ethics, IEP, EB, and CE.


Belief that all objects, events, and and values can be wholly explained in terms of factual and/or causal claims about the world, without reference to supernatural powers or authority. Prominent naturalists include Clifford and Dewey. Quine proposed a naturalistic epistemology, understood as empirical study of the origins and uses of sensory information.

Recommended Reading: Philosophical Naturalism, ed. by Peter A. French, Theodore E. Uehling, and Howard K. Wettstein (Notre Dame, 1995); Naturalism, A Critical Analysis, ed. by William Lane Craig and J. P. Moreland (Routledge, 2000); Naturalism and Ethics, ed. by Dagfinn Follesdal (Garland, 2000); Robert F. Almeder, Harmless Naturalism: The Limits of Science and the Nature of Philosophy (Open Court, 1998); Michael Rea, World Without Design: The Ontological Consequences of Naturalism (Oxford, 2002); Penelope Maddy, Naturalism in Mathematics (Oxford, 2000); , ed. by James Beilby (Cornell, 2002); David Ray Griffin, Religion and Scientific Naturalism: Overcoming the Conflicts (SUNY, 2000); and Naturalism: A Critical Analysis, ed. by William Lane Craig and J. P. Moreland (Routledge, 2000).

Also see SEP, ISM, DPM, Steven Darwall, and EB.

naturalistic fallacy

According to G. E. Moore, the mistake of identifying moral good with any natural property. Moore argued that since any such identification gives rise to an open question, it can never be correct. This constitutes a significant reason for concluding that fact and value remain irreducibly distinct.

Recommended Reading: G. E. Moore, Principia Ethica (Prometheus, 1988); Brian Hutchinson, G. E. Moore's Ethical Theory: A Reassessment (Cambridge, 2001); Dennis Rohatyn, The Reluctant Naturalist: A Study of G.E. Moore's 'Principia Ethica' (Univ. Pr. of Am., 1987); Tom Regan, Bloomsbury's Prophet: G. E. Moore and the Development of His Moral Philosophy (Temple, 1986); and Peter Simpson, Goodness and Nature: A Defense of Ethical Naturalism (Martinus Nijhoff, 1987).

Also see EB, SEP and IEP.

necessary / contingent

Distinction between kinds of truth. Necessary truth is a feature of any statement that it would be contradictory to deny. (Contradictions themselves are necessarily false.) Contingent truths (or falsehoods) happen to be true (or false), but might have been otherwise. Thus, for example:

"Squares have four sides." is necessary.

"Stop signs are hexagonal." is contingent.

"Pentagons are round." is contradictory.

This distinction was traditionally associated (before Kant and Kripke) with the distinctions between a priori and a posteriori knowledge and the distinction between analytic and synthetic judgment. Necessity may also be defined de dicto in terms of the formal logical property of tautology.

Recommended Reading: Jules Vuillemin, Necessity or Contingency? (C S L I, 1995); Colin McGinn, Logical Properties (Oxford, 2001); Alvin Plantinga, The Nature of Necessity (Clarendon, 1989); and Margaret Dauler Wilson, Leibniz' Doctrine of Necessary Truth (Harvard, 1984).

necessary / sufficient

Distinction between logical or causal conditions.

In logic, one proposition is a necessary condition of another when the second cannot be true while the first is false, and one proposition is a sufficient condition for another when the first cannot be true while the second is false. Thus, for example: "I have a dog" is a necessary condition for "My dog has fleas," and "You scored ninety-five percent" is a sufficient condition for "You received an A."

In causal relations, a necessary condition for the occurence of an event is a state of affairs without which the event cannot happen, while a sufficient condition is a state of affairs that guarantees that it will happen. Thus, for example: the presence of oxygen is a necessary condition for combustion, and the flow of electrical current is a sufficient condition for the induction of a magnetic field.

Recommended Reading: Brian McLaughlin, On the Logic of Ordinary Conditionals (SUNY, 1990); Conditionals, ed. by Michael Woods, David Wiggins, and Dorothy Edgington (Clarendon, 1997); and David Lewis, Counterfactuals (Blackwell, 2000).

Also see SEP, Norman Swartz, and CE.

negating the antecedent and the consequent

A fallacy of the form:

	p ⊃ q

	~ p ⊃ ~ q

Example: "If my daughter is sixteen, then I am over thirty. Therefore, if my daughter is not sixteen, then I am not over thirty."

This pattern of reasoning should be distinguished from legitimate cases of Transposition.

Also see FF.

 p  ~

Denial; hence, a compound statement that is true if and only if its component statement is false. Negations are symbolized here in the form:

	~ p

Example: "It is not the case that Alan is honest.".

Recommended Reading: Negation: A Notion in Focus, ed. by Heinrich Wansing (De Gruyter, 1996); What Is Negation?, ed. by Dov M. Gabbay and Heinrich Wansing (Kluwer, 1999); and George Englebretsen, Logical Negation (Van Gorcum, 1981).

negative proposition

A statement whose propositional quality is determined by the assertion that some or all members of one class of things are excluded from membership in some other class.

Examples: "No fish are birds." and "Some birds are not geese."

The first declares that the classes of fish and birds have no common members, while the second maintains that there is at least one member of the class of birds that is excluded from the class of geese.

νεικος [neikos]

Greek term for a quarrel, feud, or battle; hence, in the philosophy of Empedocles, the spirit of discord or strife in constant struggle with the benevolent influence of φιλια [philia].

Recommended Reading: Empedocles: The Extant Fragments, ed. by M. R. Wright (Hackett, 1995) and Peter Kingsley, Ancient Philosophy, Mystery, and Magic: Empedocles and Pythagorean Tradition (Oxford, 1997).

Also see PP.


Philosophical system developed by Plotinus and others. Nominally derived from Plato's metaphysics, neoplatonic philosophy regards the natural world as a series of emanations from the nature of god. During most of the medieval period, this system was the most influential version of Plato's thought.

Recommended Reading: Select Passages Illustrating Neoplatonism, tr. by E. R. Dodd (Ares, 1980); Baine Harris, The Significance of Neoplatonism (SUNY, 1976); R. T. Wallis, Neoplatonism (Hackett, 1995); and Sara Rappe, Reading Neoplatonism: Non-Discursive Thinking in the Texts of Plotinus, Proclus, and Damascius (Cambridge, 2000).

Also see IEP, Kamuran Godolek, EB, CE, and ISM.


A nineteenth- and twentieth-century movement (encouraged by Leo XIII's Aeterni Patris in 1879) that attempts to defend the philosophical and theological doctrines of Thomas Aquinas in a contemporary context. Prominent neo-Thomists include Gilson, Maritain, and Lonergan.

Recommended Reading: Gerald A. McCool, The Neo-Thomists (Marquette, 1996); The Future of Thomism: The Maritain Sequence, ed. by Deal W. Hudson, Dennis William Moran, and Donald Arthur Gallagher (Notre Dame, 1992); Conflict and Community: New Studies in Thomistic Thought, ed. by Michael B. Lukens (Peter Lang, 1993); Ralph McInerny, Characters in Search of Their Author (Notre Dame, 2001); Mind, Metaphysics, and Value in the Thomistic and Analytical Traditions, ed. by John Haldane (Notre Dame, 2002); W. Norris Clarke, The One and the Many: A Contemporary Thomistic Metaphysics (Notre Dame, 2001); and John F. X. Knasas, The Preface to Thomistic Metaphysics: A Contribution to the Neo-Thomist Debate on the State of Metaphysics (Peter Lang, 1991).

Also see CE, EB, ISM, and Jacques Maritain Center.

Neurath, Otto (1882-1945)

Austrian philosopher who founded and edited the International Encyclopedia of Unified Science. As a member of the Vienna Circle, Neurath advanced the development of logical positivism by rejecting epistemological (as well as metaphysical) assertions as meaningless. In "Protocollsätze" ("Protocol Statements") (1932) urged abandonment of efforts to ground science in uninterpreted phenomenal contents. His defence of the practical political doctrines of Marx necessitated emigration from Nazi Germany to England.

Recommended Reading: Otto Neurath, Philosophical Papers, 1913-1946 (Reidel, 1983); Otto Neurath: Philosophy Between Science and Politics, ed. by Nancy Cartwright, Jordid Cat, and Thomas Uebel (Cambridge, 1996); Encyclopedia and Utopia: The Life and Work of Otto Neurath, ed. by Elisabeth Nemeth and Friedrich Stadler (Kluwer, 1996); Logical Empiricism at Its Peak: Schlick, Carnap, and Neurath, ed. by Sahotra Sarkar (Garland, 1996); and Thomas E. Uebel, Overcoming Logical Positivism from Within: The Emergence of Neurath's Naturalism in the Vienna Circle's Protocol Sentence Debate (Rodopi, 1992).

Also see SEP, EB, and Austria-Forum.

neutral monism

Belief that both mental and physical properties are the features of substances of a single sort, which are themselves ultimately neither mental nor physical. In distinct varieties, neutral monism was defended by James and Russell.

Recommended Reading: William James: Writings 1902-1910, ed. by Bruce Kuklick (Lib. of Am., 1988); The Cambridge Companion to William James, ed. by Ruth Anna Putnam (Cambridge, 1997); Ray Monk, Bertrand Russell and the Origins of Analytical Philosophy (St. Augustine, 1997); and Mafizuddin Ahmed, Bertrand Russell's Neutral Monism.

Also see EB and DPM.

Newton, Isaac (1642-1727)

English mathematician and scientist. Newton made incomparable contributions to the development of optics and mechanics. He demonstrated the composite structure of light in Opticks: Or a Treatise of the Reflections Inflections and Colours of Light (1704). Newton's Philosophiae naturalis principia mathematica (The Mathematical Principles of Natural Philosophy) (1687) provided a comprehensive account of both celestial and terrestrial motion by reference to simple laws of motion and the notion of universal gravitation. Newton also served as Master of the Mint and President of the Royal Society.

Recommended Reading: Richard Westfall, The Life of Isaac Newton (Cambridge, 1994); The Cambridge Companion to Newton, ed. by Bernard I. Cohen and George E. Smith (Cambridge, 2002); Dana Densmore, Newton's Principia: The Central Argument (Green Lion, 1996); and Philosophical Perspectives on Newtonian Science, ed. by Phillip Bricker and R. I. G. Hughes (MIT, 1990).

Also see Richard Westfall, SEP on Newton, the Principia, Newton's philosophy, and his views on space, time, and motion, EB, David Wilkins, ELC, MMT, and WSB.


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Last modified 30 December 2011.
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