Porphyry

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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.
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 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.
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. 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,
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. 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.

Porphyry

 

(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).

WORKS

Opuscula selecta. Leipzig, 1886.
Isagoge Aristotelis Categorias Commentarium. Berlin, 1887. (Commentaria in Aristotelem Graeca, vol. 4, part 1.)

REFERENCES

Istoriia 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


Porphyry

 

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.

porphyry

[′pȯr·fə·rē]
(petrology)
An igneous rock in which large phenocrysts are enclosed in a very-fine-grained to aphanitic matrix. Formerly known as porphrite.

porphyry

Igneous rock characterized by large conspicuous crystals which are set in a matrix of finer crystals; used as decorative stone and in building construction.

porphyry

1. any igneous rock with large crystals embedded in a finer groundmass of minerals
2. Obsolete a reddish-purple rock consisting of large crystals of feldspar in a finer groundmass of feldspar, hornblende, etc.

Porphyry

original name Malchus. 232--305 ad, Greek Neo-Platonist philosopher, born in Syria; disciple and biographer of Plotinus
References in periodicals archive ?
The way down the Porphyrian Tree is not only a way from class to subclass and from shorter to longer conjunctive properties but it is also a way of specification and of increasing specificity.
The chain of specification of the categorial properties by adding and conjoining a property reminds, of course, of Aristotle's method of definition designed to place a category or another sort of existent in the Porphyrian Tree by indicating its genus proximum and then adding a differentia specifica.
Moving down a Porphyrian tree from one vertex to the next one goes from a less specific to a more specific property, which is a specification of the upper property.
The highest property of a Porphyrian Tree plays a crucial role.
As was mentioned already, they are part-whole relations in Porphyrian trees between classes and between the properties which determine the classes.
To transfer its content into a Porphyrian tree requires the formation of four categories by combining the categories of substance and accident and particular and general.
It should be noted that what Porphyrius and Simplicius call "the minimal division" cannot be the top of the Porphyrian tree.
Even in Categoriae the first substance (the particular) is taken to be the primary category which is to a certain degree equivalent with its placement at the top of the Porphyrian tree.
It is the question where to draw the line in a Porphyrian tree between the lowest categorial division and the next lower division which is not categorial.
The ten categories form just the top of a big Porphyrian tree the branches of which spread out to the most specific.
A further, linguistic argument for Porphyrian authorship is the use of [Greek text omitted] in line 8 of our text.
8) Note that miraculous transformations of Socrates, say, into a rock or some brute animal, while staying in existence, are excluded by the structure of the Porphyrian Tree as Buridan conceives of it.