1.) Nature = other than God.
2.) Most intrinsic = What all the actions of something converge on.
3.) What is most intrinsic to nature is impossible for it to achieve. It can be seen as able to achieve all that comes up to it, and so the most intrinsic can be viewed both as contiguous to this and as infinitely distant from it.
This is true in three senses of nature:
A.) In generation of whatever exists. Nature terminates with something common to all of nature. Absent this, there could not be one description of it. But what is common to all things cannot arise either from one of them or from the totality considered under the same description. Parmenides remains forever right that being cannot be generated. Nothing is more intrinsic to substance than its substantiality, but in converging on this they approach both the contiguous and the impossible, both the what is most immanent and what is infinitely transcendent.
This is the prophetic sense of Scripture’s depiction of nature as vanity of vanities. Vanity is innermost to nature because it cannot act except for the impossible. The subconscious world cannot even take the first step without trust in another and confidence that it will catch it as it runs headlong toward the abyss.
B.) In the generation of the human person. Though natural substances terminate their actions in substance and accident, the finite, end-terminating act of nature feeds off infinite nature: the flux and weather of chemical changes, the orbiting of the planets, the breeding and mutation of populations, the intrinsic infinity of the quantity of motion, division, extension and time etc. This dissipated infinity, which is only partially captured by the law of entropy, can only be justified by an intrinsically concentrated infinity of spirit perfected by its proper excellence. But spirits, like existence, are not something nature can give rise to out of her own substance.
C.) The proper excellence of the human person. Human actions are made perfect by attaining a good that it cannot attain for itself, since infinite desires are satisfied only by infinite goods and infinite goods can neither be created or claimed by right. They are possessed as free gifts or not at all.
Again, morality is impossible so long as we have to chose between the intrinsic value of an action and all of the adverse consequences we can reasonably imagine arising from it. To bring these two into harmony requires that they be underwritten by the ordering action of a being that has arranged infinite accidents in advance to work out to the benefit of the person. But such a command over accidental being can only exist in the cause of being as such, spoken of in (A).