I always liked Plotinus' approach. According to him, the intelligible world is composed of three hypostases or substances: the One, Intelligence, and the Soul:
The One: This is the supreme reality, the God of Plotinus. It is not knowledge, since knowledge requires both a knowing subject and an object known.....thus two terms, but it is also not Being itself, rather the source of Being. Plotinus also calls it the Good or the First. Nothing can truly be said about the One (except that it is One); at most, one can only describe what it is not. Yet it is what ensures the cohesion of all things. It is the source of everything. It desires nothing (for desire implies lack, and it is fullness), but because it is perfect/a sublime generosity. It tends to generate other beings that emanate from it.
Intelligence (the Spirit, Being): This is Plato’s intelligible being. It is unity multiplied in the sense that there are multiple Ideas, but together these Ideas form a unified whole. Intelligence is the principle of all justice, all virtue, all beauty. It makes reality coherent and harmonious. Intelligence contemplates the One and generates the third hypostasis.
The Soul: It is the mediation between Intelligence, from which it proceeds, and the sensible world, which emanates from it. The Soul is a kind of movement, but a logical, rational, organizing movement. It creates an ordered world and divides into individual souls (those of humans, animals, and plants). The human soul is therefore a fragment of this Soul generated by Intelligence contemplating the One. In other words, each soul is a fragment of God, meaning that God is present within each of us. The material world is the final point of divine diffusion.
There is a kind of back-and-forth movement between the summit and the base. Each hypostasis generates downward by emanation. Plotinus calls procession the process by which Intelligence proceeds from the One, the Soul proceeds from Intelligence, and the world proceeds from the Soul. The One disperses and gradually becomes obscured into the multiple. But at the same time, each element (except, of course, the One) turns back toward its principle, contemplating upward, a movement Plotinus calls conversion. Thus, the goal of each element is to regain Unity, to be enlightened. The goal of the human soul, which has fallen into the darkness of the body and of evil, is to ascend to the first principle, to the One. We must strive to know it, to merge with it. For this, one must renounce the life of the senses and reach the ecstasy in which the individual is united with God. The love of beauty and philosophy are means of attaining this ecstasy.
If interested, I strongly recommend reading "Enneads" (a collection of 54 treatises compiled by his disciple Porphyry) along with other OG Greek philosophers’ works.
