From theology, Aristotle soon moved to ethics. His work comprised the first comprehensive study of morality in Western history. He was primarily concerned with finding the underlying purpose for human existence. And he (and millions after him) thought he succeeded admirably.

Aristotle observed that all people aim at eudaemonia--well-being or exalted happiness. (Note the influence of this idea on Thomas Jefferson and the Declaration of Independence.) Aristotle believed that the life of reason leads to this happiness, manifested as a holistic, complete life. For him, virtue is a settled disposition of character and right behavior. The life of reason flourishes when we follow a balanced course, the "golden mean."

And so Aristotle wanted us to feel anger, but not too much--righteous indignation, but not irrational action. He wanted us to feel sexual attraction, but not to the point of obsession. He wanted us to seek wealth, but not so much that we become overly materialistic. And so on.

Above all, he wanted us to contemplate life. Here we find perfection in the direct knowledge of the realities revealed to us by metaphysics, mathematics, and his philosophy of nature. The more we seek to understand perfection, as revealed in the imperfect world around us, the more our souls are elevated to eudaemonia. This idea would influence spirituality for more than a thousand years.

For Aristotle, the soul is the highest principle of life and being. It possessed no previous, disembodied immortality (vs. Orpheus and Plato). And the only part of you which lives beyond your death is the "separate reason," the highest part of your soul. Your soul operates in your body through the pneuma--a life-giving heat (literally "hot air"). By this active material principle, your soul influences your body.

And so with Aristotle we arrive at the "tripart" view of humanity which is still highly influential today--body, soul, and spirit. This is not at all the biblical view of mankind (which sees us as a whole being, variously described as body, soul, and spirit, but one creation). But it is the most popular today.