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Clarke, Samuel (1675-1729)

English theologian and philosopher. In an extended correspondence with Leibniz, Clarke defended Newtonian concepts of space and time against Leibniz's relational notions. Clarke's published Discourses Concerning the Unchangeable Obligations of Natural Religion and the Truth and Certainty of Christian Revelation (1705) and Demonstration of the Being and Attributes of God (1711) employed Locke's methods of demonstration against the deists, to prove the existence and nature of god, the human obligation to worship, and the fundamental rules of morality. This view, shared by the Cambridge Platonists, became a target of Hume's criticism of natural religon.

Recommended Reading: Leibniz and Clarke: Correspondence, ed. by Roger Ariew (Hackett, 2000).

Also see SEP, EB, ELC, and MMT.


Any collection or group of things, whether natural or arbitrary. In traditional logic, classes are designated by categorical terms.

Also see EB.

clear and distinct

Features of ideas considered as mental entities, without regard for their external relation to objects they are supposed to represent. An idea is clear if its content is precise and detailed; otherwise, it is obscure. An idea is distinct if it can be distinguished from any other idea, confused if it cannot. (Although the two notions are formally distinct, they are commonly supposed to coincide, on the grounds that clarity is a necessary and sufficient condition for distinctness.) Descartes held that the clarity and distinctness of our ideas is a criterion for the truth of what we believe.

Also see SEP and EB.

Clifford, William Kingdon (1845-1879)

English mathematician and philosopher. Arguing that belief in uncertain propositions is a public act with moral consequences, Clifford endorsed a wide-ranging agnosticism, asserting in "The Ethics of Belief" (1879) that "It is wrong always, everywhere, and for anyone, to believe anything on insufficient evidence."

Also see EB and WSB.

Cockburn, Catherine Trotter (1679-1749)

English philosopher and playwright. She endorsed the philosophical methods of Locke in Defense of Mr. Locke's Essay of Human Understanding (1702). In Remarks upon some Writers in the Controversy concerning the Foundation of Moral Virtue and Moral Obligation (1743), Cockburn defended the demonstrably rational morality of Clarke against the promotion of individual self-interest emphasized by Hobbes, Shaftesbury, and Hutcheson.

Recommended Reading: The Works of Mrs. Catharine Cockburn (Thoemmes, 1998).

Also see SEP and ELC.

cogito ergo sum {Fr. je pense, donc je suis}

"I think, therefore I am." Latin translation of the first truth that Descartes believed to escape his radical method of doubt.

Recommended Reading: René Descartes, Discourse on Method and Meditations on First Philosophy, tr. by Donald A. Cress (Hackett, 1999) and The Cambridge Companion to Descartes, ed. by John Cottingham (Cambridge, 1992).

Also see SEP and EB.


The portion of human experience comprising thought, knowledge, belief, and inference (as opposed to sensation, volition, or feeling).

Recommended Reading: David Braddon-Mitchell and Frank Jackson, The Philosophy of Mind and Cognition (Blackwell, 1996) and Mind As Motion: Explorations in the Dynamics of Cognition, ed. by Robert F. Port and Timothy Van Gelder (MIT, 1998).

Also see EB.

cognitive science

Interdisciplinary effort to study and explain the processes of human thought as a system of symbol manipulation or computational rules.

For an excellent on-line guide to cognitive science, see Joe Lau.

Recommended Reading: Cognitive Science: An Introduction, ed. by David W. Green (Blackwell, 1996); A Companion to Cognitive Science, ed. by William Bechtel and George Graham (Blackwell, 1999); Patricia Smith Churchland, Neurophilosophy: Toward a Unified Science of Mind/Brain (Bradford, 1990); Barbara Von Eckardt, What is Cognitive Science? (Bradford, 1995); Justin Leiber, An Invitation to Cognitive Science (Blackwell, 1991); and Valerie Gray Hardcastle, How to Build a Theory in Cognitive Science (SUNY, 1996).

Also see EB, Barry Smith, SEP on cognitive science and neuroscience, Andrzej Chmielecki, Neb Kujundzic, Henrique de Morais Ribeiro, and DPM.

coherence theory of truth

Belief that a proposition is true to the extent that it agrees with other true propositions. In contrast with the correspondence theory's emphasis on an independent reality, this view supposes that reliable beliefs constitute an inter-related system, each element of which entails every other. Thus, such idealists as Bradley, Bosanquet, and Blanshard all defended versions the coherence theory.

Recommended Reading: Nicholas Rescher, The Coherence of Theory of Truth (U Press of America, 1987); Linda Martin Alcoff, Real Knowing: New Versions of the Coherence Theory (Cornell, 1996); Alan R. White, Truth (Anchor, 1970); and The Current State of the Coherence Theory, ed. by John W. Bender (Kluwer, 1989).

Also see SEP, EB, Michael Huemer, and DPM.

Collingwood, Robin George (1889-1943)

English philosopher. Influenced by Hegel, Cook Wilson, and Croce, Collingwood explored the implications of idealism for aesthetics and the philosophy of history in Speculum Mentis (1924), Essay on Philosophical Method (1933), The Principles of Art (1938), and The Idea of History (1946). Collingwood proposed that historical understanding be achieved through empathetic reconstruction of the thoughts that motivated the actions of historical figures.

Recommended Reading: Aaron Ridley, Collingwood (Routledge, 1999); Giuseppina D'Oro, Collingwood and the Metaphysics of Experience (Routledge, 2002); Philosophy, History and Civilization: Essays on R. G. Collingwood, ed. by David Boucher (U of Wales, 1996); and William H. Dray, History As Re-Enactment: R. G. Collingwood's Idea of History (Oxford, 1999).

Also see SEP on Collingwood and his aesthetics, EB.


Shared possession of property by all members of a society; hence, the political movement, fostered by Marx and Engels, that encourages formation of a proletarian state for the purpose of overcoming the class-structures and alienation of labor that characterize capitalistic societies.

Recommended Reading: The Communist Manifesto, ed. by Frederic L. Bender (Norton, 1988); Peter Singer, Marx: A Very Short Introduction (Oxford, 2000); Terry Eagleton, Marx (Routledge, 1999); and Introduction to Marx and Engels: A Critical Reconstruction, ed. by Richard Schmitt, Keith Lehrer, and Norman Daniels (Westview, 1997).

Also see EB and ISM.

Commutation (Comm.)

A rule of replacement of the forms:

	( p ∨ q ) ≡ ( q ∨ p )

	( p • q ) ≡ ( q • p )

Example: "Either Spot is brown or Tabby is white." is equivalent to "Either Tabby is white or Spot is brown."

Although trivial in ordinary language, the commutativity of disjunction and conjunction is a significant feature of the propositional calculus.

Also see EB.


Belief that the causal determination of human conduct is consistent with the freedom required for responsible moral agency.

Recommended Reading: Peter Van Inwagen, An Essay on Free Will (Oxford, 1986); Robert Audi, Action, Intention, and Reason (Cornell, 1993); and Hilary Bok, Freedom and Responsibility (Princeton, 1998).

Also see SEP (for) and (against), EB, and Dieter Wandschneider.


The class of all and only those things that are not included in the class designated by a categorical term. Thus, for example, things that go bump in the night is the complement of things that don't go bump in the night, and vice versa.

Also see EB.


A feature of formal systems whose axioms or rules of inference are adequate for the demonstration of every true proposition or for the justification of every valid argument. Thus, the addition of any unprovable formula to a complete system necessarily results in a contradiction. The propositional calculus is complete in this sense, but (as Gödel showed) higher-order versions of quantification theory are not.

Recommended Reading: Willard V. O. Quine, Mathematical Logic (Harvard, 1981) and Raymond M. Smullyan, Godel's Incompleteness Theorems (Oxford, 1992).

Also see EB.

complex question

The informal fallacy of framing an issue as if it involved genuine alternatives while implicitly assuming the truth of the desired conclusion.

Example: "Do you expect Peter to speak for thirty minutes or fifty? In either case, you acknowledge that he will be long-winded."

Denying the presumption that lies behind both alternatives (in this case, that Peter will speak for at least thirty minutes) would eliminate the supposed evidence that the conclusion is true.

Also see FF and GLF.

composition, fallacy of

The informal fallacy of attributing some feature of the members of a collection to the collection itself, or reasoning from part to whole.

Example: "Each of the elements in this compound (NaCl) is poisonous to human beings; therefore, this compound is itself poisonous to human beings."

Also see FF, EB, and GLF.

Comte, Auguste M. E. X. (1798-1857)

French philosopher. As an early exponent of positivism, Comte was a founder of the discipline of sociology. In an early letter to M. Valat, Comte identified a methodological culture of science. His Cours de philosophie positive (Course in Positive Philosophy) (1830-1842) traces the historical development of philosophy from its origins in theological and metaphysical thought to its culmination in observational science, especially the discipline of sociology. Comte proposed in Système de politique positive (System of Positive Polity) (1851) that political development should follow a similar path, resulting in a highly-organized communitarian state. Discours sur l'Ensemble du positivisme (A General View of Positivism) (1848) offers a convenient summary of his views.

Recommended Reading: Auguste Comte, Introduction to Positive Philosophy, ed. by Frederick Ferre (Hackett, 1988); Auguste Comte and Positivism: The Essential Writings, ed. by Gertrude Lenzer (Transaction, 1998); Comte: Early Political Writings, ed. by H.S. Jones (Cambridge, 1998); and Mary Pickering, Auguste Comte: An Intellectual Biography (Cambridge, 1993).

Also see Emmanuel Lazinier, SEP, EB, ELC, and Andy Blunden.


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