Last Updated September 5, 2023.
The Enneads by Plotinus is a work of philosophical discussion, a collection of Plotinus's ideas and theories on the nature of life, immortality, and much more. The themes are different for each section, but there are several consistent ideas that are interwoven throughout that can be analyzed.
A primary theme that runs through this work is the nature of the soul and how it separates man from beast. Plotinus gives a much more theoretical and behavioral definition of humanity and intelligence in comparison to scientific representations of species. The philosopher's idea is that intelligence and the ability to distinguish between good and evil are what give humanity their separation from beasts—and this is also his definition of the soul. By knowing good and evil and having defined morals, humans are separated and elevated above animals.
A second theme Plotinus spends a great deal of time on is the nature of the Cosmos. He believes that the stars are physical creations that portend fates. There is, in his opinion, an undeniable connection between the heavens and physical events. His second and third Enneads are intimately linked, even though the second describes exclusively physical reality (stars, the cosmos, etc) while the third deals entirely with the ideas of fate, eternity, and love. These seemingly disconnected things are, in his mind, unified—he feels that the cosmos is essentially a representation or precursor of Earthly events and affairs (as described in detail in his section "Are the stars causes?").
His third theme, explored in detail in the Fifth Ennead—however, it is prevalent throughout the text—is the idea of knowledge. He states a clear belief in universal truth, and from that is what stems the ideas of morality and ethics. This leads to the human soul (knowledge of good and evil that separates us from animals) and also leads to "inner beauty", because it allows us to become pure by following morals.