But in the Aristotelian and scholastic view of the constitution of any _corporeal_ thing, there is a danger of taking what is really only part of the essence of such a thing for the whole essence. According to this view all corporeal substance is essentially composite, constituted by two really distinct, substantial principles, primal matter (πρώτη ὕλη, _materia prima_) and substantial form (ἔιδος, μορφή) united substantially, as potential and actual principles, to form one composite nature or essence. Now the kind, or species, or specific type, to which a body belongs—_e.g._, a horse, an oak, gold, water, etc.—depends upon the substantial form which actualizes the matter or potential principle. In so far as the corporeal essence is known to us at all it is known through the form, which is the principle of all the characteristic properties and activities of that particular kind of body. Hence it is quite natural that the εἲδος, μόρφη, or _forma substantialis_ of a body should often be referred to as the specific essence of the body, though of course the essence of the body really includes the material as well as the formal factor. We may look at the essence of any being from two points of view. If we consider it as it is conceived actually to exist in the being, we call it the _physical essence_. If we consider it after the manner in which it is apprehended and defined by our intellects through generic and differentiating concepts, we call it the _metaphysical essence_. Thus, the essence of man conceived by the two defining concepts, “rational animal,” is the metaphysical essence; the essence of man as known to be composed of the two really distinct substantial principles, soul and body, is the physical essence. Understood in this way both are one and the same essence considered from different points of view—as existing in the actual order, and as conceived by the mind.(87) The physical essence of any being, understood as the constitutive principle or principles from which all properties spring, is either _simple_ or _composite_ according as it is understood to consist of one such constitutive principle, or to result from the substantial union of two constitutive principles, a material and a formal. Thus, the essence of God, the essence of a purely spiritual being, the essence of the human soul, are physically simple; the essence of man, the essences of all corporeal beings, are physically composite.