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Name given by medieval logicians to any categorical syllogism whose standard form is IAI-4.

Example: Some beloved household pets are golden retrievers, and since all golden retrievers are dogs, it must follow that some dogs are beloved household pets.

This is one of only fifteen forms of syllogistic reasoning that are always valid.

Ding an sich

German phrase for thing in itself.

Diogenes (400-325 BCE)

Greek philosopher. As one of the original Cynics, Diogenes both preached and practiced a life of complete self-sufficiency, utter simplicity, and total disregard for the conventional morality of what he took to be a corrupt human society. Diogenes was the teacher of Zeno of Citium.

Recommended Reading: The Cynics: The Cynic Movement in Antiquity and Its Legacy, ed. by R. Bracht Branham and Marie Odile Goulet-Caze (California, 2000) and D. R. Dudley, A History of Cynicism (Ares, 1980).

Also see IEP, EB, and ELC.

direct realism

Theory of perception according which we perceive material objects directly, without the mediation of ideas or sensory representations. Although it is also called "naïve" realism, this view often requires a sophisticated defence, especially in its attempts to account for the occurrence of hallucinations and perceptual error.

Recommended Reading: Thomas Reid, An Inquiry into the Human Mind on the Principles of Common Sense, ed. by Derek Brookes (Penn. State, 2001); H. H. Price, Perception (Greenwood, 1982); and Moltke S. Gram, Direct Realism: A Study of Perception (Nijhoff, 1983).

directive use of language

Communication that aims to bring about or to forestall the performance of some action.

Example: "Don't forget to take out the trash."


Name given by medieval logicians to a categorical syllogism whose standard form may be designated as IAI-3.

Example: Some nutritious dinners are vegetarian delights, and all nutritious dinners are well-rounded meals, so some well-rounded meals are vegetarian delights.

This is one of fifteen forms in which any syllogism is valid.

 p  q  p

A compound statement that is true whenever either one or both of its component statements (the disjuncts) are true. Disjunctions are symbolized here in the form:

	p ∨ q

Example: "Either the switch is off or the bulb is burned out."

Also see SEP and EB.

Disjunctive Syllogism (D.S.)

A rule of inference of the form:

	p ∨ q

	~ p


Example: "Either Ellen brought him to the party or Keith did. But Ellen didn't. So, Keith brought him to the party."

The validity of this pattern of reasoning is evident from a simple truth-table.


A tendency or propensity to respond in specific ways to particular circumstances. Things are commonly supposed to have dispositional features only in virtue of their possession of intrinsic or non-dispositional properties. Thus, for example, sugar is soluble in water (even when it is not in water) because of its chemical composition. Ryle maintained that mental states can be wholly analyzed as dispositions of human bodies.

Recommended Reading: Gilbert Ryle, The Concept of Mind (Chicago, 2000).

Also see SEP and Paul Raymont.

distribution of terms

A feature that categorical terms come to have by virtue of their use in a specific categorical proposition. The term is distributed if the proposition refers to every member of the class it designates, unidistributed if it does not. Thus, the subject term is distributed in all and only universal propositions; the predicate term is distributed in all and only negative propositions.

Distribution (Dist.)

A rule of replacement of the forms:

	[ p • ( q ∨ r ) ] ≡ [ ( p • q ) ∨ ( p • r ) ]

	[ p ∨ ( q • r ) ] ≡ [ ( p ∨ q ) • ( p ∨ r ) ]

Example: "Paul is tall, and so is either Susan or James." is equivalent to "Either Paul and Susan are tall or Paul and James are."

The logical relationship between pairs of this sort may be demonstrated by the construction of a truth-table.

Also see .

division, fallacy of

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

Example: "Today's newspaper has a lot of grocery ads, so each page of today's newspaper has a lot of grocery ads."

Also see FF and GLF.

double aspect theory

Belief that mental properties and events on the one hand and physical properties and events on the other hand are irreducibly distinct features or aspects of one and the same thing that exhibits them both. Spinoza, for example, maintained that thought and extension are distinct attributes of the one existing substance that is "god or nature."

Recommended Reading: Keith Campbell, Body and Mind (Notre Dame, 1984); Genevieve Lloyd, Routledge Philosophy Guidebook to Spinoza and the Ethics (Routledge, 1996); and Michael Della Rocca, Representation and the Mind-Body Problem in Spinoza (Oxford, 1996).

Also see DPM and EB.

Double Negation (D.N.)

A rule of replacement of the form:

	p ≡ ~ ~ p

Example: "Alan is clever" is equivalent to "It is not the case that Alan is not clever."

Although trivial in ordinary language, this rule is vital for the completeness of the propositional calculus.

doubt, method of

The starting-point for Descartes's philosophy. He used perceptual illusions, the dream problem, and the possibility of a deceiving god to show the uncertainty of many common beliefs. Only the cogito then survives as an indubitable foundation for knowledge.

Recommended Reading: René Descartes, Discourse on Method and Meditations on First Philosophy, tr. by Donald A. Cress (Hackett, 1999); Janet Broughton, Descartes's Method of Doubt (Princeton, 2002); E. M. Curley, Descartes Against the Skeptics (Iuniverse, 1999); and The Cambridge Companion to Descartes, ed. by John Cottingham (Cambridge, 1992).

Also see Lex Newman and Encéphi.

δοξα [dóxa]

Greek term for opinion, belief, or judgment, as opposed to systematic knowledge {Gk. επιστημη [epistêmê]}. According to Plato, this limited awareness of the sensible world encompasses the lower portion of the divided line. In Aristotle's works on logic, the same terms are used to distinguish contingent from necessary truths about the world.

Recommended Reading: F. E. Peters, Greek Philosophical Terms: A Historical Lexicon (NYU, 1967).

Also see PP.

dualism, mind-body

Belief that mental things and physical things are fundamentally distinct kinds of entities. As a solution to the traditional mind-body problem, dualism derives especially from Descartes and his followers in the seventeenth century. Variations on this theme (including interactionism, parallelism, and epiphenomenalism) arise when dualists try to explain why events in the supposedly separate realms of mind and body seem so well-coordinated with each other.

Recommended Reading: Marleen Rozemond, Descartes's Dualism (Harvard, 1998); Case for Dualism, ed. by John R. Smythies and John Beloff (Books Demand, 1989); Raia Prokhovnik, Rational Woman: A Feminist Critique of Dualism (Routledge, 1999); and John Cottingham, Descartes (Routledge, 1999).

Also see SEP, IEP, DPM, EB, Conald V. Poochigian, and ISM.

Du Bois, William Edward Burghardt (1868-1963)

American historian and sociologist. After completing his education with a Ph.D. from Harvard, Du Bois embarked on a long and distinguished career as a university professor and social activist. His The Souls of Black Folk (1903) was a penetrating analysis of the origins, practices, and consequences of racial discrimination in the United States. Du Bois also participated in efforts at social reform, founding the National Association fot the Advancement of Colored People in 1910 and editing the influential journals Crisis and Phylon. Details of Du Bois's life are to be found in his autobiography, Dusk of Dawn (1940).

Recommended Reading: The Oxford W. E. B. Du Bois Reader, ed. by Eric J. Sundquist (Oxford, 1996); W. E. B. Du Bois, The Souls of Black Folk: Authoritative Text, Contexts, Criticism, ed. by Henry Louis Gates, Jr. and Terri Hume Oliver (Norton, 1999); W. E. B. Du Bois, Writings: The Suppression of the African Slave-Trade: The Souls of Black Folk: Dusk of Dawn: Essays: Articles from the Crisis (Library of America, 1996); and W. E. B. Du Bois on Race and Culture: Philosophy, Politics, and Poetics, ed. by Bernard W. Bell, Emily Grosholz, and James B. Stewart (Routledge, 1996).

Also see EB and ELC.

Duhem, Pierre M. M. (1861-1916)

French historian and philosopher of science. In La Théorie physique: son objet et sa structure (The Aim and Structure of Physical Theory) (1906) Duhem maintained that every scientific theory is an exercise in metaphysical speculation, verified or falsified by the predictive power it is shown to have as a systematic whole.

Recommended Reading: Pierre Duhem: Essays in History and Philosophy of Science, ed. by Roger Ariew and Peter Barker (Hackett, 1996) and R. N. D. Martin, Pierre Duhem: Philosophy and History in the Work of a Believing Physicist (Open Court, 1991).

Also see SEP, EB, and MMT.

Dummett, Michael A. E. (1925- )

English philosopher and logician. The essays collected in Truth and other Enigmas (1978) and The Seas of Language (1993) defend an intuitionist philosophy of mathematics and emphasize the linguistic foundations of epistemology. Dummett is also the foremost English interpreter of Frege in such works as Frege: Philosophy of Language (1973), The Interpretation of Frege's Philosophy (1981), and Frege: Philosophy of Mathematics (1991).

Recommended Reading: Michael Dummett, Frege and Other Philosophers (Oxford, 1996); Michael Dummett, The Logical Basis of Metaphysics (Harvard, 1993); and Michael Dummett, Origins of Analytical Philosophy (Harvard, 1996).

Also see EB.

δυναμις [dynamis]

Greek term for power or force, used by presocratic philosophers in reference to the qualities or features of material elements. Aristotle later used the term to signify potentiality, or the capacity for undergoing change. The neoplatonic tradition, on the other hand, developed a conception of personified causal agents.

Recommended Reading: F. E. Peters, Greek Philosophical Terms: A Historical Lexicon (NYU, 1967).

Also see Christopher Philip Long and PP.

Durkheim, Émile (1858-1917)

French philosopher and sociologist. Durkheim argued that since society is something more than merely a collection of individual human beings, it follows that social events cannot be explained wholly in biological or psychological terms. This insight was a significant impetus for the independence of sociology as a science. His major writings include Éléments de sociologie (1889), Les Règles de la méthode sociologique (Rules for Sociological Method) (1895), De la division du travail social (The Division of Labor in Society) (1893), and Le Suicide (Suicide: A Study in Sociology) (1897). Durkheim criticized pragmatism in Pragmatism and Society (1914).

Recommended Reading: Emile Durkheim, On Morality and Society: Selected Writings, ed. by Robert N. Bellah (Chicago, 1975); Gianfranco Poggi, Durkheim (Oxford, 2000); and Steven Lukes, Emile Durkheim, His Life and Work: A Historical and Critical Study (Stanford, 1985).

Also see EB, ELC, and Andy Blunden.


What we ought to do; an action that people are required to perform; the practical content of a moral obligation.

Recommended Reading: Immanuel Kant, Grounding for the Metaphysics of Morals, tr. by James W. Ellington (Hackett, 1993); W. D. Ross, The Right and the Good (Hackett, 1988); and Philip Stratton-Lake, Kant, Duty, and Moral Worth (Routledge, 2001).

Also see IEP and CE.

Dworkin, Ronald Myles (1931- )

American political philosopher. In Taking Rights Seriously (1977) and Law's Empire (1986) Dworkin defends a version of legal positivism that relies heavily upon the principled adjudication of disputes by the judiciary. His treatment of concrete legal issues concerning abortion and euthanasia is to be found in Life's Dominion (1993). "Objectivity and Truth: You'd Better Believe It" argues that a moderate notion of objectivity secures the objectivity of moral claims.

Recommended Reading: Ronald Dworkin, Freedom's Law: The Moral Reading of the American Constitution (Harvard, 1997); The Philosophy of Law, ed. by Ronald M. Dworkin (Oxford, 1977); Stephen Guest, Ronald Dworkin (Stanford, 1992); and Ronald Dworkin and Contemporary Jurisprudence, ed. by Marshall Cohen (Rowman & Littlefield, 1984).

Also see Simon Blackburn.


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