Compiled in the 3rd century AD by his student Porphyry, "The Enneads" unfolds Plotinus' study of the principles of the universe. This work is organized into 54 treatises, which are in turn more largely grouped into six books, which form the foundational concepts of Neo-Platonism. The first Ennead deals principally with ethical topics and human subjects, such as happiness, virtue, beauty, and evil. The second and third Enneads discuss mainly physical reality and cosmology, including heaven, substance, fate, eternity, time, stars, and guardian spirits. The fourth Ennead focuses exclusively on the soul, while the fifth Ennead delves into comprehensible reality and knowledge, particularly on the human intellect. Finally, the sixth Ennead considers Being and One. Overall, "The Enneads" reveal the organized thoughts of one of the last great philosophers of antiquity, a man who believed in the ability of the human soul to ascend through ever higher levels of existence toward a supreme perfection. In synthesizing philosophical thought with a mystic and nearly religious belief, this work would come to powerfully influence the Christian and Islamic theology that would follow.