Plotinus’ (205–270) system of thought was arranged in the Enneads, which was made up of six groups of nine essays: the first three groups are about the physical world and human interaction with it; the fourth group is about the soul; the fifth is about intelligence; and the sixth is about the One. Although Plotinus thought he was a faithful student of Plato, he in fact added ideas from Aristotle, the stoics, and his own philosophical imagination.

Plotinus divided the Platonic imperceptible world of forms into three parts: the One, Intelligence, and the Soul. The One is above everything that is, because it is the highest principle of being and causation. As a principle, however, the One is everything, in everything. Because the One is a unity, it has no thought or awareness, which requires a separation between thinking and the object thought. Paradoxically, the One is both completely ignorant, lacking awareness even of itself, but also, in its own way, aware of everything that it has created.

After the One, there is Intelligence, which corresponds to Plato’s specific forms, taken as a totality. Intelligence has an idea for everything that exists. Intelligence also contains number, which corresponds to souls, and it contains original matter. However, there is not an endless multiplication of ideas because, as the stoics proclaimed, every so often the entire world is destroyed.