propositional attitude Psychological state expressed by a verb that may take a subordinate clause beginning with “that” as its complement. Verbs such as “believe,” “hope,” “fear,” “desire,” “intend,” and “know”
all express propositional attitudes. The linguistic contexts created by their use are typically referentially opaque (see intentionality) in the sense that the substitution of co-referential expressions within them may change the “truth value” (true or false) of the containing sentence. Thus, to use Ber¬ trand Russell’s example, though it is true that Peter believes that Walter Scott was a Scotsman, it may be false that he believes that the author of Waverley (who is Scott) was a Scotsman.
propositional calculus Formal system of propositions and their logi¬ cal relationships. As opposed to the predicate calculus, the propositional calculus employs simple, unanalyzed propositions rather than predicates as its atomic units. Simple (atomic) propositions are denoted by lower¬ case Roman letters (e.g., p, q), and compound (molecular) propositions are formed using the standard symbols a for “and,” v for “or,” z> for “if . . . then,” and —■ for “not.” As a formal system, the propositional calcu¬ lus is concerned with determining which formulas (compound proposi¬ tion forms) are provable from the axioms. Valid inferences among propositions are reflected by the provable formulas, because (for any for¬ mulas A and B) Ad B is provable if and only if B is a logical conse¬ quence of A. The propositional calculus is consistent in that there exists no formula A in it such that both A and —■ A are provable. It is also com¬ plete in the sense that the addition of any unprovable formula as a new axiom would introduce a contradiction. Further, there exists an effective procedure for deciding whether a given formula is provable in the sys¬ tem. See also logic, predicate calculus, laws of thought.
propositional function Sentencelike expression that may be thought of as obtained from a sentence by substituting variables for constants occurring in the sentence. For example, “x was a parent of y” may be thought of as obtained from “Adam was a parent of Abel.” A proposi¬ tional function therefore has no truth-value, becoming true or false only when its free variables are replaced by constants of appropriate syntactic categories (e.g., “Abraham was a parent of Isaac”).
proprietary colony Type of settlement in British North America (1660-90). To repay political and financial debts, the British crown, beginning with Charles II, awarded supporters vast tracts of land in colo¬ nial New York, New Jersey, Pennsylvania, Maryland, and the Carolinas. The proprietors were to supervise and develop the colonies, which became successful enterprises. By 1690 concern about the colonies’ growing inde¬ pendence from control by British officials led to the end of proprietary grants.
proprioception V.pro-pre-o-'sep-shonX Perception of stimuli relating to position, posture, equilibrium, or internal condition. Receptors (nerve end¬ ings) in skeletal muscles and on tendons provide constant information on limb position and muscle action for coordination of limb movements. Awareness of equilibrium changes usually involves perception of gravity. In humans, gravity, position, and orientation are registered by tiny grains called otoliths moving within two fluid-filled sacs in the inner ear in response to any change in position or orientation. Their motion is detected by sense hairs. Rotation is detected by the inertial lag of fluid in the semi¬ circular canals acting on the sense hairs. The central nervous system inte¬ grates signals from the canals to perceive rotation in three dimensions. See also sense.
propylaeum N.pra-po-'le-om, .pro-po-'le-omV In ancient Greek archi¬ tecture, a structure forming an entrance or gateway to a sacred enclosure, usually consisting, at the least, of a porch supported by columns both out¬ side and within the actual gate. The term is often used in the plural (pro- pylaea). The most famous example is the great Propylaea designed by Mnesicles for the Athenian Acropolis. The name propylaea was also applied to various 18th-19th-century Neoclassical and Romantic monu¬ mental gateways.
proscenium \pro-'se-ne-3m\ In a theatre, the frame or arch separating the stage from the auditorium, through which the action of a play is viewed. In ancient Greek theatres, the proskenion was an area in front of the SKENE that eventually functioned as the stage. The first permanent proscenium in the modern sense was built in 1618 at the Farnese Theatre in Parma. Though the arch contained a stage curtain, its main purpose was to pro¬ vide a sense of spectacle and illusion; scene changes were carried out in view of the audience. Not until the 18th century was the curtain com¬ monly used to hide scene changes. The proscenium opening was of par¬ ticular importance to 19th-century realist playwrights, for whom it served as a picture frame or an invisible wall through which the audience expe¬ rienced the illusion of spying on the characters.
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prose ► protectionism I 1555
prose Literary medium distinguished from poetry especially by its greater irregularity and variety of rhythm and its closer correspondence to the patterns of everyday speech. Though it is readily distinguishable from poetry in that it does not treat a line as a formal unit, the significant differences between prose and poetry are of tone, pace, and sometimes subject matter.
prose poem Work in prose that has some of the technical or literary qualities of poetry (such as regular rhythm, definitely patterned structure, or emotional or imaginative heightening) but that is set on a page as prose. The form took its name from Charles Baudelaire’s Little Poems in Prose (1869). Other writers of prose poems include, in the 19th century, Stephane Mallarme, Arthur Rimbaud, Friedrich Holderlin, Novalis, and Rainer Maria Rilke, and in the 20th, Amy Lowell (in her “polyphonic prose”) and such contemporary poets as John Ashbery.
prosecutor Government attorney who presents the state’s case against the defendant in a criminal prosecution. In some countries (France, Japan), public prosecution is carried out by a single office. In the U.S., states and counties have their own prosecutors. Only at the federal level is the sys¬ tem unitary; the U.S. attorney general’s office appoints a U.S. attorney for each federal district. In most state and local jurisdictions, prosecutors are elected to office. Whether elected or appointed, prosecutors are often sub¬ ject to political pressures. A prosecutor takes charge of the investigation once a crime has been committed, presents evidence at a hearing before a grand jury, and questions witnesses during the trial. See also independent counsel.
Proserpina See Persephone
prosody Vpra-so-de, 'pra-z9-de\ Study of the elements of language, especially metre, that contribute to rhythmic and acoustic effects in poetry. The basis of “traditional” prosody in English is the classification of verse according to the syllable stress of its lines. Effects such as rhyme scheme, alliteration, and assonance further influence a poem’s “sound meaning.” Nonmetrical prosodic study is sometimes applied to modern poetry, and visual prosody is used when verse is “shaped” by its typographical arrangement. Prosody also involves examining the subtleties of a poem’s rhythm, its “flow,” the historical period to which it belongs, the poetic genre, and the poet’s individual style.
Prosser, Gabriel See Gabriel
prostaglandin \,pras-t3-'glan-d3n\ Any of a class of organic com¬ pounds that occur in many animal tissues and have diverse hormonelike effects in animals (see hormone). Their common chemical structure is derived from a fatty acid with 20 carbon atoms. They have important effects on blood pressure, blood clotting, pain sensation, and reproduction mechanisms, but one prostaglandin may have different and even opposite effects in different tissues. They hold promise for treating heart disease and viral diseases and may be useful in contraception. Some substances that inhibit prostaglandin synthesis (see aspirin) are useful in controlling pain, asthma attacks, or anaphylactic shock or as anticoagulants.