Such are the topics considered in the First Ennead; which thus contains what relates to morals.
In the Second Ennead are grouped the writings that treat of Physics, of the World, and of all that it contains. They are:
| 1. | (Of the World), | [40.] |
| 2. | Of the (Circular) Motion (of the Heavens), | [14.] |
| 3. | Of the Influence of the Stars, | [52.] |
| 4. | (Of both Matters) (Sensible and Intelligible), | [12.] |
| 5. | Of Potentiality and Actuality, | [25.] |
| 6. | Of Quality (and of Form), | [17.] |
| 7. | Of Mixture, Where there is Total Penetratration, | [37.] |
| 8. | Of Vision. Why do Distant Objects Seem Smaller? | [35.] |
| 9. | (Against Those Who say that the Demiurgic Creator is Evil, as well as The World Itself), Against the Gnostics, | [33.] |
The Third Ennead, which also relates to the world, contains the different speculations referring thereto. Here are its component writings:
| 1. | Of Destiny, | [3.] |
| 2. | Of Providence, the First, | [47.] |
| 3. | Of Providence, the Second, | [48.] |
| 4. | Of the Guardian Spirit who was Allotted to Us, | [15.] |
| 5. | Of Love, | [50.] |
| 6. | Of the Impassibility of Incorporeal Things, | [26.] |
| 7. | Of Eternity of Time, | [45.] |
| 8. | Of Nature, of Contemplation, and of the One, | [30.] |
| 9. | Different Speculations, | [13.] |
We have gathered these three Enneads into one single body. We have assigned the book on the Guardian Spirit Who has been Allotted to Us, in the Third Ennead, because this is treated in a general manner, and because it refers to the examination of conditions characteristic of the production of man. For the same reason the book on Love was assigned to the First Ennead. The same place has been assigned to the book on Eternity and Time, because of the observations which, in this Ennead, refer to their nature. Because of its title, we have put in the same group the book on Nature, Contemplation, and the One.
After the books that treat of the world, the Fourth Ennead contains those that refer to the soul. They are:
| 1. | Of the Nature of the Soul, the First, | [4.] |
| 2. | Of the Nature of the Soul, the Second, | [21.] |
| 3. | Problems about the Soul, the First, | [27.] |
| 4. | Problems about the Soul, the Second, | [28.] |
| 5. | (Problems about the Soul, the Third, or) Of Vision, | [29.] |
| 6. | Of Sensation, of Memory, | [41.] |
| 7. | Of the Immortality of the Soul, | [2.] |
| 8. | Of the Descent of the Soul into the Body, | [6.] |
| 9. | Do not all Souls form a Single Soul? | [8.] |
The Fourth Ennead, therefore, contains all that relates to Psychology.
The Fifth Ennead treats of Intelligence. Each book in it also contains something about the principle superior to intelligence, and also about the intelligence characteristic of the soul, and about Ideas.