LONGINUS, DIONYSIUS CASSIUS, a celebrated Greek critic and grammarian, was, according to Fabricius, grandson of Cassius Longinus, who is mentioned by Plutarch (Symp. ix. 1); but this is a mere conjecture, unsupported by any adequate proof. The precise period of his birth is unknown, though it is not unlikely that it took place about A. D. 213, in the reign of Caracalla, as he may be supposed to have preceded by at least twenty years his pupil Porphyry, who was born A. D. 233. There is no doubt that his death took place A. D. 273, when the Emperor Aurelian took Palmyra. The place of his birth is also a matter of much uncertainty, as it is nowhere distinctly stated. The circumstance of his understanding the Syrian language, and his uncle being from Emesa in Syria, has caused some to fix on that city as his native place; and others have suspected, though with still less appearance of probability, that he was from Palmyra. His uncle Fronto enjoyed considerable reputation as a teacher of philosophy at Athens; and, amongst other pupils, he had Philostratus, who is known to us by his life of the philosopher and prophet Apollonius of Tyana, which is still preserved. It would appear that Fronto was much attached to his nephew, whom he made his heir; and from him Longinus most probably derived the rudiments of his education. In his earlier years we find, from a fragment of one of his works preserved by Porphyry in his life of Plotinus, that he travelled much, and enjoyed the opportunity of becoming acquainted with all the most distinguished philosophers of his time. He gives the names of upwards of twenty, but, with the exception of Ammonius Saccas, Origen, Plotinus, and Amelius, their celebrity was not sufficient to rescue them from oblivion. Ammonius taught the Platonic philosophy at Alexandria in Egypt, and at this time appears to have enjoyed a high reputation. The doctrines Longitude, which he advocated, and his particular system, are known to us from the works of his pupil Plotinus, and the epitome of Hierocles in Photius. (Cod. ccxiv. p. 550.) The philosopher Origen, the master of Longinus, is not to be confounded with the Christian bishop of the same name, who was born at Alexandria, A. D. 185. After Longinus had made himself completely master of the philosophy of Plato, which he preferred to that of every other sect, he took up his residence at Athens, and devoted himself to the instruction of youth in grammar and philosophy. Here Porphyry attended him, and derived much of that information which he afterwards employed against the Christian religion. After a long residence at Athens, he proceeded to the East, and joined Zenobia, queen of Palmyra, who had a little before succeeded to the government of the kingdom upon the death of her husband Odenathus. He became her preceptor in the Greek language, and she even consulted him respecting the administration of her affairs. Zenobia was persuaded by her courtiers that she was sufficiently powerful to refuse obedience to the commands of Aurelian, who had some time before succeeded to the Roman empire. Aurelian was more particularly amazed by the haughty style of a letter which was sent by Zenobia in answer to his demands, and which was said to have been dictated by Longinus. This letter is found in the life of Aurelian by Flavius Vopiscus (Aug. Script. vol. ii. p. 174, ed. Bipont.). Palmyra was taken after an obstinate siege, and Aurelian was ungenerous enough to punish him by death for the insult which had been offered to his dignity by the letter he had dictated. Longinus died without indulging in vain regrets, and in a manner worthy of his character as a philosopher, consoling the companions of his misfortunes. (Zosim. i. 56.) He was the author of many works of criticism, but, with the exception of a few fragments, and of his treatise Περὶ Τῆς Συλλογίας, On the Sublime, they have all perished. This treatise is addressed to his friend Posthumus Terentianus, and is an able disquisition on the various sources from which sublimity in writing is derived, illustrated by examples selected from the works of the most distinguished authors of antiquity. The Old Testament was not unknown to him, as he has quoted as one of the noblest specimens of the sublime, the celebrated passage in Genesis: "And God said, Let there be light; and there was light." We find also in a fragment (E. Cod. MS. to Vat.) that he ranks Paul of Tarsus, as he styles the apostle, with Demosthenes and the more celebrated orators of Greece. He was no doubt acquainted with the doctrines of Christianity; and the noble sentiments which he at times expresses may not unreasonably be ascribed to this circumstance. In the epilogue to his treatise, he speaks most feelingly of the corruption which pervaded every part of the world, and of the little attention which was paid to the cultivation of the intellect. The moral degeneracy of the age he in a great measure ascribes to the absence of free institutions, and quotes the well-known lines of the Odyssey, which Pope has thus translated:— Jove fixed it certain, that whatever dayMakes man a slave, takes half his worth away. It is remarkable that such sentiments should be found at this period of the world; but there can be no doubt that they were the genuine expression of his feelings. This treatise has been frequently edited, and one of the best editions is that by Hudson, Oxford, 1710. It has also been edited by Weiske, Weigel, 1809; and by Toup, Oxford, 1778. It has been translated into English by Smith, 1739; and into German by J. G. Schlosser, Leipzig, 1781, and by Von Heincken, Basel, 1784.