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The characteristic of words or phrases whose meaning is not determined with precision. Use of one or more vague terms typically renders it impossible to establish the truth or falsity of the sentences in which they appear.

Example: "The temperature is warm today." is difficult to evaluate because there is no clear borderline between "warm" and "not warm".

Note the difference between vagueness and ambiguity.

Recommended Reading: Timothy Williamson, Vagueness (Routledge, 1996); Vagueness: A Reader, ed. by Rosanna Keefe and Peter Smith (MIT, 1999); Roy Sorensen, Vagueness and Contradiction (Oxford, 2001); Linda Claire Burns, Vagueness: An Investigation into Natural Languages and the Sorites Paradox (Kluwer, 1991); and Rosanna Keefe, Theories of Vagueness (Cambridge, 2001).

Also see SEP, FF, and Loretta Torrago.

Vaihinger, Hans (1852-1933)

German philosopher. In Die Philosophie des Als-Ob (The Philosophy of As-If) (1911)) Vaihinger extrapolated from Kant's epistemology (as understood by Schopenhauer) the notion that all of our concepts—including those involved in both science and morality—are nothing more than useful fictions. This outlook was a significant influence on the psychological theories of Alfred Adler. Vaihinger described the origins of his theory in Wie die Philosophie des Als Ob entstand (1924).

Recommended Reading: Hans Vaihinger, Commentar zu Kants Kritik der reinen Vernunft (Garland, 1992) and Andrea Wels, Die Fiktion des Begreifens und das Begreifen der Fiktion: Dimensionen und Defizite der Theorie der Fiktionen in Hans Vaihingers Philosophie des Als Ob.

Also see Christopher Adair-Toteff and EB.

valid / invalid

The most crucial distinction among deductive arguments and the inferences upon which they rely.

In a valid argument, if the premises are true, then the conclusion must also be true. Alternatively: it is impossible for the premises of a valid argument to be true while its conclusion is false.

All other arguments are invalid; that is, it is possible for their conclusions to be false even when their premises are true. Thus, even the most reliable instances of inductive reasoning fall short of deductive validity.

Recommended Reading: Graham Priest, Logic: A Very Short Introduction (Oxford, 2000) and Patrick Suppes, Introduction to Logic (Dover, 1999).

Also see EB.

Valla, Lorenzo (1407-1457)

A leader of the Italian Renaissance. Valla's humanistic philosophy criticized the sterility of scholastic logical distinctions and tried to synthesize Christian principles with Stoic and Epicurean thought. In De libero arbitratio (Of Free Choice) Valla noted the incompatibility of divine omnipotence with human freedom.

Recommended Reading: The Treatise of Lorenzo Valla on the Donation of Constantine, tr. by Christopher B. Coleman (Toronto, 1993) and Renaissance Philosophy of Man: Petrarca, Valla, Ficino, Pico, Pomponazzi, Vives, ed. by Ernst Cassirer, Paul Oskar Kristeller, and John H. Randall (Chicago, 1956).

Also see SEP, EB, and ELC.

value {Ger. Wert}

Worth in some respect, which may be either intrinsic or extrinsic to the things that have it. The most general philosophical issue in the study of value (axiology) is whether values arise from objective or subjective features of experience.

Noncognitivists defend a strict distinction between fact and value, and many contemporary thinkers challenge the presumption that human knowledge can ever be genuinely free of value-judgments.

Recommended Reading: Michael J. Zimmerman, The Nature of Intrinsic Value (Rowman & Littlefield, 2001); Joel J. Kupperman, Value...and What Follows (Oxford, 1999); Gilbert Harman, Explaining Value: And Other Essays in Moral Philosophy (Clarendon, 2000); Forms of Value and Valuation, ed. by John W. Davis and Rem B. Edwards (Univ. Pr. of Am., 1992); Joseph Raz, Value, Respect, and Attachment (Cambridge, 2001); Sven Ove Hansson, The Structure of Values and Norms (Cambridge, 2001); Robin Attfield, Value, Obligation, And Meta-ethics (Rodopi, 1995); and Elizabeth Anderson, Value in Ethics and Economics (Belknap, 1996).

Also see SEP on value and value theory.


In a system of formal logic, any symbol that—unlike a constant—designates generally. Thus, the propositional calculus employs statement variables, while quantification theory makes use of individual variables.

Veblen, Thorsten (1857-1929)

American social philosopher whose work contributed to the sociology of knowledge by emphasizing the influence of material conditions on the development of human thought. Veblen's critical analysis of American capitalism is evident in The Theory of the Leisure Class (1899), and The Higher Learning in America (1918) comments on the devastating effect of treating higher education as a business.

Recommended Reading: Thorstein B. Veblen, (Kelley, 1964); John Patrick Diggins, Thorstein Veblen (Princeton, 1999); Michael Keaney and Douglas Fitzgerald Dowd, Thorstein Veblen (Transaction, 2000); and Samuel Schneider, An Identification, Analysis and Critique of Thorstein B. Veblen's Philosophy of Higher Education (Edwin Mellen, 1998).

Also see EB.

Venn, John (1834-1923)

British logician. In Symbolic Logic (1881) Venn applied the insights of Boole, Euler, and others in developing a diagrammatic method for testing the validity of categorical syllogisms. He also contributed to the development of modern theories of probability in The Logic of Chance (1867) and The Principles of Empirical or Inductive Logic (1889).

Also see EB.

Venn diagrams

John Venn's modern pictorial method of representing and evaluating the validity of categorical syllogisms. The classes designated by the terms of a syllogism are represented by overlapping circles, with shading and  ×s indicating, respectively, the impossibility and existence of their common members.

Recommended Reading: Sun-Joo Shin, The Logical Status of Diagrams (Cambridge, 1994).

Also see EB.

verbal dispute

The appearance of disagreement between parties who have not resolved the ambiguity of one or more key terms. Agreement on the definition of these terms eliminates a verbal dispute completely.

verecundiam, argumentum ad

The fallacy of making an illicit appeal to authority.

verifiability principle

The claim that the meaning of a proposition is just the set of observations or experiences which would determine its truth, so that an empirical proposition is meaningful only if it either actually has been verified or could at least in principle be verified. (Analytic statements are non-empirical; their truth or falsity requires no verification.) Verificationism was an important element in the philosophical program of logical positivism.

Recommended Reading: A. J. Ayer, Language, Truth, and Logic (Dover, 1946); Carl Gustav Hempel, Selected Philosophical Essays, ed. by Richard C. Jeffrey (Cambridge, 2000); C. J. Misak, Verificationism: Its History and Prospects (Routledge, 1995); and Michael Friedman, Reconsidering Logical Positivism (Cambridge, 1999).

Also see IEP and EB.


Latin word for truth.

Also see PP.


German term for reason. Kant distinguished reine Vernunft ("pure reason") or abstract thought from praktische Vernunft ("practical reason") or volition.


German term for understanding.


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