Longi'nus, Diony'sius Ca'ssius（Διονύσιος Κάσσιος Λογγῖνος), a very distinguished Greek philosopher of the third century of our era. His original name seems to have been Dionysius; but, either because he entered into the relation of client to some Cassius Longinus, or because his ancestors had received the Roman franchise, through the influence of some Cassius Longinus, he bore the name of Dionysius Longinus, Cassius Longinus, or in the complete form given at the head of this article. He was born about A. D. 213, and was killed in A. D. 273, at the age of sixty. His native place is uncertain; some say that he was born at Palmyra, and others call him a Syrian or a native of Emesa. The belief that he was of Syrian origin is only an inference from the fact that his mother was a Syrian woman, and from an obscure passage in Vopiscus (Aurelian. 30), from which it may be inferred that he was conversant with the Syriac language. But it is clear that these circumstances prove nothing, for he may have learned the Syriac language either from his mother or during his subsequent residence at Palmyra. There is more ground for believing that Longinus was born at Athens, for Suidas (s. v. Φρόντων) states that Phronto of Emesa, the uncle of Longinus, taught rhetoric at Athens, and on his death in that place left behind him Longinus, the son of his sister. It would seem that this Phronto took especial care of the education of his nephew, and on his death-bed he instituted him as his heir. In the preface to his work περὶ τέλους, which is preserved in Porphyrius's life of Plotinus (p. 127), Longinus himself relates that from his early age he made many journeys with his parents, that he visited many countries, and became acquainted with all the men who at the time enjoyed a great reputation as philosophers, and among whom the most illustrious are Ammonius Saccas, Origen, Plotinus, and Amelius. Of the first two Louginus was a pupil for a long time, though they did not succeed in inspiring him with any love for that kind of speculative philosophy of which they were the founders. Longinus in his study of philosophy went to the fountain-head itself, and made himself thoroughly familiar with the works of Plato; and that he was a genuine Platonist is evident from the character of his works. or rather, fragments still extant, as well as from the commentaries he wrote on several of Plato's dialogues; and the few fragments of these commentaries which have come down to us, show that he had a clear and sound lead, and was free from the allegorical fancies in which his contemporaries discovered the great wisdom of the ancients. His commentaries not only explained the subject-matter discussed by Plato, but also his style and diction. This circumstance drew upon him the contempt and ridicule of such men as Plotinus, who called him a philologer, and would not admit his claims to be a philosopher. (Porphyr. Vit. Plot. p. 116; Proclus, ad Plat. Tim. p. 27.) After Longinus had derived all the advantages he could from Ammonius at Alexandria, and the other philosophers whom he met in his travels, he returned to Athens, where he had been born and bred. He there devoted himself with so much zeal to the instructions of his numerous pupils, that he had scarcely any time left for the composition of any literary production. The most distinguished among his pupils was Porphyrius, whose original name was Malchus, which Longinus changed into Porphyrius, i. e. the king, or the man clad in purple. At Athens he seems to have lectured on philosophy and criticism, as well as on rhetoric and grammar (Eunap. Porphyr. init.; Porphyr. Vit. Plot. p. 131; Vopisc. Aurelian. 30; Suid. s. v. Λογγῖνος), and the extent of his information was so great, that Eunapius calls him "a living library" and "a walking museum ;" but his knowledge was not a dead encumbrance to his mind, for the power for which he was most celebrated was his critical skill (Phot. Bibl. Cod. 259; Sopat. Proleg. in Aristid. p. 3; Suid. s. vr. Πορφύριος, Λογγῖνος), and this was indeed so great, that the expression κατὰ Λογγῖνον κρίνειν became synonymous with "to judge correctly." (Hieronym. Epist. 95; Theophylact. Epist. 17.) After having spent a considerable part of his life at Athens, and composed the best of his works, he went to the East, either for the purpose of seeing his friends at Emesa or to settle some of his family affairs. It seems to have been on that occasion that he became known to queen Zenobia of Palmyra, who, being a woman of great talent, and fond of the arts and literature, made him her teacher of Greek literature. As Longinus had no extensive library at his command at Palmyra, he was obliged almost entirely to abandon his literary pursuits, but another sphere of action was soon opened to him there; for when king Odenathus had died, and Zenobia had undertaken the government of her empire, she availed herself most extensively of the advice of Longinus, and it was he who, being an ardent lover of liberty, advised and encouraged her to shake off the Roman yoke, and assert her dignity as an independent sovereign. In consequence of this, Zenobia wrote a spirited letter to the Roman emperor Aurelian. (Vopisc. Aurelian. 27.) In A. D. 273, when Aurelian took and destroyed Palmyra, Longinus had to pay with his life for the advice which he had given to Zenobia. (Vopisc. Aurelian. 30; Suid. s. v. Λογγῖνος.) This catastrophe must have been the more painful to Longinus, since the queen, after having fallen into the hands of the Romans, asserted her own innocence, and threw all the blame upon her advisers, and more especially upon Longinus. But he bore his execution with a firmness and cheerfulness worthy of a Socrates. (Zosimus, 1.56.)
WorksLonginus was unquestionably by far the greatest philosopher of the age, and stands forth so distinct and solitary in that age of mystic and fanciful quibblers, that it is impossible not to recognise in him a man of excellent sense, sound and independent judgment, and extensive knowledge. He had thoroughly imbibed the spirit of Plato and Demosthenes, from whom he derived not only that intellectual culture which distinguished him above all others, but also an ardent love of liberty, and a great frankness both in expressing his own opinions and exposing the faults and errors of others. (Porphyr. Vit. Plot. p. 126.)
Περὶ ὕψους, a great part of which is still extant, surpasses in oratorical power every thing that was ever written after the time of the Greek orators, and he, like Cicero among the Romans, is the only Greek who not only knew how to teach rhetoric, but was able by his own example to show what true oratory is. Besides the Greek and Syriac languages, he was also familiar with the Latin, as we must conclude from his comparison of Cicero with Demosthenes (Περὶ ὕψ. § 12; comp. Suid. s. v. Αἰωνοάριος; Tzetz. Posthom. p. 75.) In his private life he seems to have been a man of a very amiable disposition; for although his pupil Porphyrius left him, declaring that he would seek a better philosophy in the school of Plotinus, still Longinus did not show him any ill-will on that account, but continued to treat him as a friend, and invited him to come to Palmyra. (Porphyr. Vit. Plot. pp. 120, 124, 131.) He was, and remained throughout his life, a pagan, though he was by no means hostile either to Judaism or Christianity.