It was a long time before Plotinus committed his thoughts to writing; and gave the world a copy of his inimitable mind. That light which was shortly to illuminate mankind, as yet shone with solitary splendour, or at best beamed only on a beloved few. It was now, however, destined to emerge from its sanctuary, and to display its radiance with unbounded diffusion. But a disciple like Porphyry, was requisite to the full perfection of its appearance. Amelius was indeed laborious, but he was at the same time verbose. He neither appears to have possessed the inquisitive spirit, nor the elegant genius of Porphyry and his commentaries were too voluminous to be exquisitely good. Porphyry gives a singular specimen of his endurance of labour, when he informs us that he committed to writing almost all the dogmas of Numenius, and retained a very considerable part of them in his memory. He was not, however, though an excellent philosopher, calculated to urge Plotinus to write, or to assist him in writing; but this important task was reserved for Porphyry, who, in the words of Eunapius, “ like a Mercurial chain let down for the benefit of mortals, by the assistance of universal erudition, explained every thing with clearness and precision.” Plotinus, indeed, began to write in the first year of the Emperor Gallienus; and he continued to note such questions as occurred to him, for the ten following years, in the last of which he became acquainted with Porphyry, who was at that time in the thirtieth year of his age. He had then composed one-and-twenty books, which were in the hands but of a few: for the edition was difficult to be procured, and was not universally known. Besides, Plotinus was neither hasty nor rash in his publications ; but he gave those only to the light, which had been approved by a mature and deliberate judgement. The one-and-twenty books we have just mentioned, after various inscriptions, at length obtained the following titles.

On the Beautiful. Ennead I. lib. 6 On the Immortality of the Soul. IV. 7 On Fate. III. 1 On the Essence of the Soul. IV. 1 On Intellect, Ideas, and Being. V. 9 On the Descent of the Soul into Bodies. IV. 8 How things posterior to the First, proceed from the First, and on the One. V. 4. Whether all Souls are one ? IV. 9 On the Good, or the One. VI. 9 On the three Hypostases that rank as the Principles of Things. V. 1 On the Generation and Order of Things posterior to the First. V. 2 On the two Matters (i.e. the Intelligible and the Sensible). II. 4 Various Considerations. III. 9 On the Circular Motion of the Heavens. II. 2 On the Daemon allotted to us. III. 4 On the reasonable Exit from the present Life. I. 9 On Quality. II. 6 Whether there are Ideas of Particulars. V. 7. On the Virtues. I. 2. On Dialectic. I. 3 How the Soul is said to be a medium between an impartible and partible Essence. IV. 2

These one-and-twenty books were finished when Porphyry first became acquainted with Plotinus; and when this great man was fifty-nine years old. During the six years in which Porphyry was his companion as well as disciple, many questions of a very abstruse nature were discussed in their philosophical conversations, which, at the joint request of Porphyry and Amelius, Plotinus committed to writing, and produced from their investigation, two elaborate and admirable books, On true being, demonstrating that it is every where one and the same whole. “Ennead” VI. lib. 4, 5. And afterwards he wrote two others, one of which shows, That the nature which is beyond being is not intellective, and what that is which is primarily, and also that which is secondarily intellective. “Ennead” V. 6. But the other is, On that which is in capacity, and that which is in energy. “Ennead” II. 5. He likewise wrote the following books:

On the Impassivity of Incorporeal Natures. Ennead III. 6. On the Soul, two Books. IV. 3, 4. On the Sold, a third Book, or On the Manner in which we see. IV. 5. On Contemplation. III. 8. On Intelligible Beauty. V. 8. That Intelligibles are not external to Intellect; and concerning Intellect and the Good. V. 5. Against the Gnostics. II. 9. On Numbers. VI. 6. “Why things seen at a distance appear to be small. II. 8. Whether Felicity consists in an extension of Time. I. 5. On Total Mixture. II. 7. How the multitude of Ideas subsists, and concerning the Good. VI. 7. On the Voluntary. VI. 8. On the World. II.1. On Sense and Memory. IV. 6. On the Genera of Beings, three Books. VI. 1, 2, 3. On Eternity and Time. III. 7.

But while Porphyry resided in Sicily, and about the fifteenth year of the Emperor Gallienus, Plotinus composed the five following Books, which he sent to Porphyry for his revision.

On Felicity. Ennead I. 4. On Providence, two Books. III. 2, 3. On Gnostic Hypostases, and that which is beyond them. IV. 3. On Love. III. 5.

These books were transmitted to Porphyry in the first year of the Emperor Claudius' reign. And about the beginning of the second year, and a little before his death, he sent him the following, and the last:

On what things are Evil, and whence Evils originate. Ennead I. lib. 8. Whether the stars effect any thing. II. 3. What Man is, and what Animal is ? I. 1. On the First Good, and other Goods. I. 7.

The whole amount therefore, of the books written by Plotinus, connecting the preceding with those just enumerated, is fifty-four, which Porphyry has divided into six enneads, assigning, agreeably to the meaning of the word, nine books to every ennead. But they bear evident marks, says Porphyry, of the different periods, at which they were composed. For the first one-and-twenty, which were written in the former part of his life, if compared with the next in order, seem to possess an inferior power, and to be deficient in strength. But those composed in the middle of his life, exhibit the vigour of power, and the acme of perfection. And such with a few exceptions are the four-and-twenty we have already enumerated. The last nine, however, which were composed in the decline of life, bear the marks of remitted energy, and drooping vigour. And this the four last exhibit more evidently than the preceding five.