Porphyry(redirected from Porphyrian)
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porphyry(pôr`fərē), igneous rock composed of large, conspicuous crystals (phenocrysts) and a groundmass in which the phenocrysts are embedded. Some authorities consider the expression "porphyritic rock" better usage than porphyry, since the term refers only to the texture of the rock—not its chemical, physical, or mineralogical composition or color. The texture is important in the determination of the circumstances under which the rock formed. The phenocrysts vary in size; the groundmass may be either glassy or made up of coarse or fine granules or crystals. The varieties of porphyry are many, the specimens being named by the character of the phenocrysts in the groundmass. They are found in main classes of igneous rocks, e.g., in granite, syenite, diorite, gabbro, and peridotite. Porphyritic felsites and porphyritic basaltsbasalt
, fine-grained rock of volcanic origin, dark gray, dark green, brown, reddish, or black in color. Basalt is an igneous rock, i.e., one that has congealed from a molten state.
..... Click the link for more information. are widely distributed. The porphyritic texture indicates two separate stages of solidification. In the first phase the phenocrysts form in the molten mass; in the second, the molten mass itself crystallizes into a solid. Porphyritic texture is especially common in extrusions, e.g., in lava.
Porphyry(pôr`fĭrē), c.232–c.304, Greek scholar and Neoplatonic philosopher. He studied rhetoric under Cassius Longinus and philosophy under PlotinusPlotinus
, 205–270, Neoplatonist philosopher. A native of Egypt, perhaps of Roman descent, he went to Alexandria c.232 to devote himself to philosophy. For 10 years he was a dedicated disciple of Ammonius Saccas.
..... Click the link for more information. . He later lectured in Rome on the philosophy of Plotinus and was the teacher of the Neoplatonist IamblichusIamblichus
, d. c.330, Syrian philosopher, a leading exponent of Neoplatonism. A pupil of Porphyry, he was deeply impressed by the doctrines of Plotinus. In his own teachings he combined with Plato's ideas many of those of Pythagoras and much that was mystical and even magical,
..... Click the link for more information. . He wrote lives of Pythagoras and of Plotinus and edited the Enneads of Plotinus. He wrote extensively against Christianity and on rhetorical and literary themes. His most influential work is the Isagoge, an introduction to the logic of Aristotle, which became a standard medieval text.
(Porphyrios). Born circa 233, in Tyre; died 304, in Rome. Ancient Greek philosopher. Representative of Neo-platonism.
A disciple of Plotinus, Porphyry published his master’s works and wrote a description of his life. Porphyry won fame chiefly as a commentator on the works of Plato and Aristotle. His treatise, an Introduction to the Categories of Aristotle, was the principal source through which Aristotelian logic was studied during the Middle Ages. The treatise was also known as the Isagoge [Quinque voces, or On the Five Voices], a reference to the five criteria of a concept: genus, species, differentia, essential attributes, and nonessential or separable accidents. Porphyry’s Categories was supplemented with commentaries and translated many times. (Boethius translated it into Latin.)
In logic the tree of Porphyry illustrates the multilevel subordination of the concepts of genus and species in dichotomous division. Porphyry also wrote many works on mathematics, astronomy, history, and grammar. The lengthy treatise Against the Christians, which contains early examples of biblical criticism, was burned in 448. Only fragments of the work were preserved (see A. B. Ranovich, Classical Critics of Christianity, Moscow, 1935).
WORKSOpuscula selecta. Leipzig, 1886.
Isagoge Aristotelis Categorias Commentarium. Berlin, 1887. (Commentaria in Aristotelem Graeca, vol. 4, part 1.)
REFERENCESIstoriia filosofii, vol. 1. Moscow, 1940.
Kleffner, A. J. Porphyrins, der Neuplatoniker und Christenfeind. Paderbom, 1896.
Bidez, J. Vie de Porphyre le philosophe néo-platonicien. Ghent-Leipzig, 1913.
A. F. LOSEV
the general term for effusive and paleotypal acidic rocks that have porphyritic textures. Porphyry was originally the name of a unique red rock with large white orthoclase phenocrysts that was widely used for decoration and sculpture in ancient Rome. Orthoclase porphyry, or orthopyre, which closely resembles trachyte, is distinguished from quartz porphyry, which closely resembles liparite (rhyolite). Typically, porphyry has a glassy groundmass replaced by felsite (a submicroscopic graphic granite aggregate) and microlites of albite or orthoclase, as well as by phenocrysts of orthoclase or orthoclase and quartz. The groundmass also often contains biotite and hornblende. Porphyry is commonly found in ancient volcanic strata.