The leading proponent of Neoplatonism, Plotinus was the last of the great early Greek philosophers. His metaphysic stressed the need to transcend this world, know the Divine Mind, and become reunited with the One. Plotinus's hierarchical system is set forth in his Enneads (253-70), collected by one of his students, Porphyry, at the beginning of the fourth century. Although opposed to the Gnostics and other Christian sects, Plotinus greatly influenced Christian philosophers, notably Saint Augustine and Saint Thomas Aquinas, and aspects of his philosophy have become incorporated into Catholic theology.
Most of what is known about Plotinus comes from a biography written by Porphyry about 301 titled On the Life of Plotinus and the Order of His Books. According to Porphyry, Plotinus cared little for his earthly form and was reticent when it came to revealing his past. Nevertheless, some details of his life are known. Plotinus was born in Lycopolis, Egypt. From about age twenty-seven to thirty-nine he studied in Alexandria under Ammonius Saccas, a Platonist often considered the founder of Neoplatonism. Ammonius exerted a profound influence on Plotinus's thought. Plotinus fought against the Persians with Emperor Gordian III; after Gordian was murdered, Plotinus moved to Antioch, and then to Rome. Ammonius had always refused to put his own teachings in writing, and Plotinus followed this practice for his first ten years in Rome. He did not begin writing until age forty-nine. He was a friend of the Emperor Gallienus (253-68) and at one time the two apparently considered establishing a city to be run according to Platonic principles.
The essays which make up the Enneads are believed to have stemmed from Plotinus's lectures to students at seminars. Porphyry organized the essays into six books of nine chapters each, arranged by subject matter: Book IV, for example, deals with the Soul, while Book VI deals with Being. Plotinus emphasized a state of unselfconscious contemplation, in which an individual's true self achieves union with the One,—a condition he himself achieved only occasionally and for fleeting moments. The One is at the top of Plotinus's hierarchy, represents pure unity, and is sometimes translated as the Good or the Divine Mind. It defies expression in words. Below that is the Intellect, and below that the Soul. The Soul links the Intellect to the material world, a world that is really made up of little more than images. Matter is at the lowest level of the hierarchy. Plotinus showed disdain for much of the earthly world and for art that attempts to copy reality. Porphyry informs us that Plotinus did not form his letters with any regard for neatness, did not divide his syllables correctly, and paid no attention to spelling. A. H. Armstrong says that “anyone who reads the Enneads will soon discover that Plotinus writes in a Greek very much of his own, which is certainly not bad or barbarous, but is highly unconventional and irregular.” Armstrong warns that it is dangerous to emend Plotinus's text, therefore, because of the possibility of introducing error.
Plotinus's teachings were not popular in his own lifetime, nor were they intended to be: he presupposed great knowledge in his readers and his style was difficult even for the best educated. Much of the scholarly work involving Plotinus deals with clarifying his sometimes oblique and often abstract texts. John Bussanich writes that the study of Plotinus “is an irresistibly intriguing and tantalizingly difficult enterprise. Behind every sentence, every phrase we can sense a vigorous intelligence at work, one which is, at the same time, supremely certain of its direction and purpose, but which also strains for expression.” Plotinus did not believe it was possible to fully understand or adequately convey ultimate truth through language. Some critics have suggested that Plotinus uses symbolism and metaphorical language in his writings to try to overcome the limitations of words; Sara Rappe explores Plotinus's deliberate use of metaphor to hint at what it is like to achieve union, and Steven K. Strange contends that Plotinus believed that metaphor is the only means of speaking about otherworldly reality. Bertrand Russell sees Plotinus's philosophy as an attempt to mentally overcome the physical disasters of Rome—to, in effect, leave this world by concentrating on another. He emphasizes the beauty of Plotinus's philosophy and states that Plotinus was the last philosopher for centuries who was not hostile to beauty and pleasure. Scholars are actively engaged in trying to determine to what degree Plotinus was influenced by the works of his predecessors and to what extent his ideas are original. E. R. Dodds writes that the Enneads “converge almost all the main currents of thought that come down from 800 years of Greek speculation; out of it there issues a new current, destined to fertilize minds as different as those of Augustine and Boethius, Dante and Meister Eckhart, Coleridge, Bergson, and Mr. T. S. Eliot.”