Essence is not a positive being apart from the existence of which it is the limitation, but it is definitely a positive principle of philosophy when understood as the intrinsic limitation of esse . Its function can be designated by affirmative terms, contraction, refraction, channeling of perfection, specification, determination. All essences are modes of esse . The created essence is not its esse , it is the intrinsic limitation of esse , the prism through which the intelligible riches and perfections of esse are refracted and contracted to this kind of being. Carlo is setting before our eyes a many-faceted metaphysical gem, but each facet leads us to the luminous heart of metaphysics.
Essence is a certain capacity to exist.
It is this or that capacity to exist. Essences don't exist. We know essences by abstracting them from existents as the intrinsic limitations of existence. And we know existence not first in its purity without limit, but in this or that existent about which we can assert that it exists. But it exists in this or that way or mode.