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Price, Henry Habberly (1899-1984)

British philosopher who defended a comprehensive theory of the relation between sense-data and material objects in Perception (1932), Hume's Theory of the External World (1946), and Thinking and Experience (1953).

Recommended Reading: The Collected Works of Henry H. Price, ed. by Martha Kneale (Thoemmes, 1997) and Philosophical Interactions With Parapsychology: The Major Writings of H. H. Price on Parapsychology and Survival, ed. by Frank B. Dilley (Palgrave, 1995).

Also see EB.

Price, Richard (1723-1791)

Welsh philosopher and theologian. Price was an early proponent of an intuitionistic moral theory in his A Review of the Principle Questions and Difficulties in Morals (1758), where—in opposition to Hume—he argued that moral obligation has a rational foundation. Price's firm commitment to individual liberty made him a vocal supporter of the American and French Revolutions. The actuarial principles expounded in Observations on Reversionary Payments (1771) provided a mathematical foundation for the development of the modern insurance industry.

Recommended Reading: W. D. Hudson, Reason and Right: A Critical Examination of Richard Price's Moral Philosophy (Anchor, 1984).

Also see EB.

Prichard, H. A. (1871-1947)

English philosopher whose posthumously-published essays influenced a generation of Oxford philosophers. Prichard defended moral intuitionism in "Does Moral Philosophy Rest on a Mistake?" (1921) and Moral Obligation (1949). Price also offered support for perceptual realism in Knowledge and Perception (1950).

Recommended Reading: H. A. Prichard, Kant's Theory of Knowledge (Garland, 1994).

Also see SEP.

prima facie

Latin phrase meaning "at first sight." Thus, in the ethics of W. D. Ross, a prima facie duty is a defeasible presumption that we are obligated to perform an action.

Recommended Reading: W. D. Ross, The Right and the Good (Hackett, 1988) and Mary Anne Warren, Moral Status: Obligations to Persons and Other Living Things (Clarendon, 1997).

Also see IEP and EB.

primary / secondary qualities

Distinction between perceived aspects of things. The primary qualities are intrinsic features of the thing itself (its size, shape, internal structure, mass, and momentum, for example), while the secondary qualities are merely its powers to produce sensations in us (its color, odor, sound, and taste, for example). This distinction was carefully drawn by Galileo, Descartes, Boyle, and Locke, whose statement of the distinction set the tone for future scientific inquiry. But Foucher, Bayle, and Berkeley argued that the distinction is groundless, so that all sensible qualities exist only in the mind of the perceiver.

Recommended Reading: Selected Philosophical Papers of Robert Boyle (Hackett, 1991); Peter Alexander, Ideas, Qualities and Corpuscles: Locke and Boyle on the External World (Cambridge, 1983); E. J. Lowe, Routledge Philosophy Guidebook to Locke on Human Understanding (Routledge, 1995); P. M. S. Hacker, Appearance and Reality: A Philosophical Investigation into Perception and Perceptual Qualities (Blackwell, 1986); Colin McGinn, The Subjective View: Secondary Qualities and Indexical Thoughts (Clarendon, 1983); and Austen Clark, Sensory Qualities (Oxford, 1996).

Also see IEP and John Locke.

Pringle-Pattison, Andrew Seth

See Seth (Pringle-Pattison), Andrew.

private language argument

Wittgenstein's contention that it is impossible for an isolated individual to employ language, since a single person could not have adequate criteria for following linguistic rules. This argument is commonly taken as a refutation of solipsism.

Recommended Reading: Ludwig Wittgenstein, Philosophical Investigations, tr. by G. E. M. Anscombe (Prentice Hall, 1999); Saul A. Kripke, Wittgenstein on Rules and Private Language (Harvard, 1984); Marie McGinn, Routledge Philosophy Guidebook to Wittgenstein and the Philosophical Investigations (Routledge, 1997); Owen Roger Jones, The Private Language Argument (Anchor, 1979); and Andreas Roser, Die Privatsprache der Privatsprachenkritik bei Ludwig Wittgenstein.

Also see SEP and IEP.


The likelihood that an event will occur, expressed quantitatively by a number ranging from 0 (impossible) to 1 (certain). Initial probabilities are often assigned either on the classical assumption that every possible outcome is equally likely to occur or by careful empirical observation of the relative frequency with which events have actually occurred in the past. The likelihood of alternative and joint occurrences can be calculated directly from these initial values.

Recommended Reading: Patrick Suppes, Foundations of Probability With Applications (Cambridge, 1996); Richard Jeffrey, Probability and the Art of Judgment (Cambridge, 1992); Donald Gillies, Philosophical Theories of Probability (Routledge, 2000); David Howie, Interpreting Probability: Controversies and Developments in the Early Twentieth Century (Cambridge, 2002); Henry Kyburg, Studies in Subjective Probability (Krieger, 1980); and The Theory of Gambling and Statistical Logic, ed. by Richard A. Epstein (Academic, 1995).

Also see Rudy Garns, SEP, EB, Richard Jeffrey, and SEP.

problematic / assertoric / apodeictic

Distinction among the modalities of propositions. A problematic proposition states what is possible; an assertoric proposition states what is actual; and an apodeictic proposition states what is necessary. For example:

"A novel could be larger than a dictionary." is problematic.

"Atlanta is larger than Knoxville." is assertoric.

"142 is larger than 37." is apodeictic.


A formal demonstration of the validity of a deductive argument.

Recommended Reading: Proof, Logic and Formalization, ed. by Michael Detlefsen (Routledge, 1992); Donald C. Benson, The Moment of Proof: Mathematical Epiphanies (Oxford, 2000); Sara Negri and Jan van Plato, Structural Proof Theory (Cambridge, 2001); Lance J. Rips, The Psychology of Proof: Deductive Reasoning in Human Thinking (Bradford, 1994); and Handbook of Proof Theory, ed. by Samuel R. Buss (Elsevier, 1998).

Also see SEP on proof theory and provability and EB.


What is conveyed by a declarative sentence used to make a statement or assertion. Each proposition is either true or false, though in a particular instance we may not know which it is.

Recommended Reading: Gabriel Nuchelmans, Judgment and Proposition (Royal Netherlands Academy, 1983) and Philip L. Peterson, Fact, Proposition, Event (Kluwer, 1997).

Also see SEP on propositions, singular propositions, and structured propositions.

propositional calculus

A formal system of symbolic logic concerned with compound statements formed by the use of truth-functional logical connectives.

Recommended Reading: Richard L. Epstein, Propositional Logics: The Semantic Foundations of Logic (Wadsworth, 2000); Hans Kleine Buning and Theodor Lettman, Propositional Logic: Deduction and Algorithms (Cambridge, 1999); and Howard Pospesel and William G. Lycan, Introduction to Logic: Propositional Logic (Prentice Hall, 1999).

Also see SEPEB.

Protagoras of Abdera (485-415 BCE)

Presocratic philosopher; one of the sophists. Protagoras is best known for the relativistic assertion that human beings are "the measure of all things."

Recommended Reading: G. S. Kirk and J. E. Raven, The Presocratic Philosophers: A Critical History With a Selection of Texts (Cambridge, 1988) and Jonathan Barnes, The Presocratic Philosophers (Routledge, 1982).

Also see IEP, EB, and ELC.

Proudhon, Pierre-Joseph (1809-1865)

French anarchist. Proudhon's Qu'est-ce que la propriété? (What is Property?) (1840) defined property as theft and demanded that individual workers be allowed to control the means of their own production. Proudhon was notoriously anti-feminist, arguing in La Pornocratie (Pornocracy) that sexual equality and economic independence for women would undermine traditional marriage.

Recommended Reading: Pierre-Joseph Proudhon, The General Idea of the Revolution in the Nineteenth Century (Pluto, 1989); John Ehrenberg, Proudhon and His Age (Prometheus, 1996); and George Woodcock, Pierre-Joseph Proudhon: A Biography (Black Rose, 1996).

Also see Anarchist Archives, Dana Ward, EB, and ELC.

prudence {Gk. φρνησις [phrónêsis]; Lat. prudentia}

Practical wisdom; sound judgment in everyday life as distinguished from theoretical wisdom. According to Aristotle, this ability to discover and carry out the proper goals of human life is a vital element in moral deliberation.

Recommended Reading: Daniel Mark Nelson, The Priority of Prudence: Virtue and Natural Law in Thomas Aquinas and the Implications for Modern Ethics (Penn. State, 1992) and Douglas J. Den Uyl, The Virtue of Prudence (Peter Lang, 1991).

Also see CE.

ψυχη [psychê]

Greek term for soul as the essential principle of life and the locus of consciousness. Although used pre-philosophically simply in reference to the "breath of life," the term was associated by presocratic philosophers, including especially Anaxagoras, with an explanatory principle. Pythagorean thought proposed that the ψυχη be understood as the persistent element in the life of an individual. Plato expanded upon this view with a detailed account of the tripartate soul, with associated human virtues, and an argument for the immortality of its rational component. Aristotle restored a broader sense of the term, using it for the several functions characteristic of living things generally. Neoplatonic thinkers made it the cosmic principle of all motion.

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

Also see PP.

Pufendorf, Samuel (1632-1694)

German political philosopher. In De jure naturae et gentium (On the Law of Nature and Nations) (1672) and De officio hominis et civis (On the Duty of Man and Citizen) (1673) Pufendorf defended a social contract with significant attention to the regulative force of natural law.

Recommended Reading: Grotius, Pufendorf and Modern Natural Law, ed. by Knud Haakonssen (Dartmouth, 1999) and The Political Writings of Samuel Pufendorf, ed. by L. Carr Craig and Michael J. Seidler (Oxford, 1995).

Also see SEP, IEP, EB, and ELC.


Deliberate infliction of harm as a moral sanction against offenders. Punishment may be understood, designed, and applied according to any of the three major varieties of normative theory:

Recommended Reading: Nigel Walker, Why Punish? (Oxford, 1991); David A. Hoekema, Rights and Wrongs: Coercion, Punishment and the State (Susquehanna, 1987); Punishment, ed. by John Simmons, Marshall En, Joshua Cohen, and Thomas Scanlon (Princeton, 1994); Louis P. Pojman and Jeffrey Reiman, The Death Penalty (Rowman & Littlefield, 1998); and David Garland, Punishment and Modern Society: A Study in Social Theory (Chicago, 1993).

Also see SEP on punishment and legal punishment, EB, and IEP.

Putnam, Hilary (1926- )

American philosopher. Author of Mind, Language, and Reality (1975) and Reason, Truth, and History (1981). Putnam decisively rejects the verificationism of the logical positivists. Although he had earlier defended functionalist accounts of human nature and the external world, Putnam criticized them in Representation and Reality (1988) and Realism with a Human Face (1990), preferring a more moderate position he calls "internal realism."

Recommended Reading: Hilary Putnam, Renewing Philosophy (Harvard, 1995); Hilary Putnam, The Threefold Cord (Columbia, 2001); Hilary Putnam: Pragmatism and Realism, ed. by James Conant and Urszula M. Zeglen (Routledge, 2002); The Twin Earth Chronicles: Twenty Years of Reflection on Hilary Putnam's 'The Meaning of 'Meaning'', ed. by Andrew Pessin and Sanford Goldberg (M. E. Sharpe, 1996); and Mark Q. Gardiner, Semantic Challenges to Realism: Dummett and Putnam (Toronto, 2000).

Also see DPM, Bas van Fraassen, EB, and SEP.

Pyrrho of Elis (365-270 BCE)

Greek philosopher who originated classical skepticism. Since there are plausible arguments for both sides of any issue, Pyrrho argued, the only rational practice is to suspend all judgment, abandon worries of every kind {Gk. αταραξια [ataraxia]}, and live comfortably in an appreciation of the appearances. His teachings were preserved and amplified by his pupil Timon of Philius.

Recommended Reading: Edwyn Bevan, Stoics and Skeptics (Ares, 1980) and Richard Bett, Pyrrho, His Antecedents, and His Legacy (Oxford, 2000).

Also see SEP, IEP, EB, and ELC.

Pythagoras (585-497 BCE)

Legendary presocratic philosopher whose followers studied mathematics, astronomy, and music in their pursuit of lives of harmony with the natural world. The work of the Pythagoreans is known to us only through fragmentary reports in the writings of other philosophers. According to Aristotle, for example, the Pythagoreans held that the ultimate constituents of all material objects are numbers, perhaps understood as geometrical points. Apparently they also held with religious devotion that souls are naturally immortal and therefore transmigrate at death to other human or animal bodies.

Recommended Reading: Edouard Schure, Pythagoras and the Delphic Mysteries (Kessinger, 1997); The Pythagorean Sourcebook and Library, ed. by Kenneth Sylvan Guthrie (Phanes, 1991); Dominic J. O'Meara, Pythagoras Revived: Mathematics and Philosophy in Late Antiquity (Oxford, 1991); and John Strohmeier and Peter Westbrook, Divine Harmony: The Life and Teachings of Pythagoras (Berkeley Hills, 1999).

Also see IEP, SEP on Pythagoras and Pythagoreanism, John Burnet, EB, ISM, ELC, WSB, and MMT.


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Last modified 30 December 2011.
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