In my interactions with Peter Escalante over at Wedgewords, the topic has turned, for the time being, from defining what the Church is to the only slightly less challenging task of defining what nature and natural law is. Since Peter has asked me to explain my understanding of natural law, I've decided to give it a shot.... This is my first attempt to reflect systematically on this question and offer a proper definition from start to finish, so this may turn out to be incoherent or heretical or something. Feel free to let me know. I have avoided defining my position via explicit reference to any other theologians because that would pose too much temptation to lazy shorthand, but you are welcome to come in and slap labels on what I've said: "Aha! So you're just a Barthian Anabaptist Hegelian" or something of that sort, to help me resolve my identity crisis.
To cover such a broad sweep concisely, it was necessary to make this all rather abstract, and as I have not mastered the scholastic art of being simultaneously very abstract and very precise, you may be puzzled as to exactly what I am trying to say at certain points. Please push me for clarification, and I will try to provide it if possible, though I can't guarantee it will be:
1. There is such a thing as natural law.
a) When God created the world, he intended for it to operate in a certain way, he intended it for a particular destiny. This destiny was communion with God, not of course in a narrowly-construed way that would simply instrumentalize nature--the beauty and goodness of the creation was an end in itself for the Creator--but such that the goodness of creation’s end, although not reducible into communion with God, is not separable from it either; creation achieves its full potential and perfection when it is ordered toward the love of God.
b) natural law is, quite simply, that which is necessary for creation to achieve its perfection, to successfully reach the end appointed for it. When creatures turn away from natural law, they become perverted from their true end and perfection, their created destiny; when they observe it, they are oriented properly toward their telos, the perfection of their own natures in congruence with the love of God
c) natural law is, therefore, implanted in every creature at creation, as an instinct or understanding of its purpose which it freely wills to obey.
2. Natural law is Christologically-determined from the first
a) the original creation, although without corruption, was not perfect; it had yet to be perfected, because it was not intended to be static, but to mature, through a history involving further action by both Creator and creatures. The state of the original creation, therefore, although congruent with its final end, does not in itself reveal the perfection of nature and the natural law.
b) Christ is the firstfruits over all creation, the one in whom all things consist, the Last Adam who reveals the destiny of the first, the true image of the invisible God who reveals what man, created in the image of God, is meant to be. For him and through him and to him are all things. In short, Jesus Christ reveals for us and leads us toward the true destiny of creation. It is only by union with him and conformity with him that we attain unto the full stature of our humanity.
c) Therefore, we cannot properly define natural law except by reference to the revelation in Jesus Christ that illumines the true sense of nature.
3. Natural law is knowable in part, but not in full
a) from creation, man had implanted in him an adequate, though not perfect, understanding of the natural law. His being was oriented toward its proper destiny, but had not yet matured into full understanding of it. This knowledge was limited thus both by immaturity and by the finitude of the human understanding, which could not perfectly grasp the entirety of the natural law in its first principles and its necessary deductions.
b) at the Fall, man lost full fellowship with God, and with it, his conformity to the mind of God that enabled true understanding of himself and his purpose in the world. Creation itself was cursed with decay as a result of this dislocation between humanity and God, and thus both humanity and the rest of creation ceased to be oriented toward their true end, but, detached from it, became distorted and no longer conformed perfectly to natural law. Nevertheless, inasmuch as nature continued, though in a wounded state, natural law continued to govern it. Man’s knowledge of it was impaired now by his lack of fellowship with God, fellowship which gave insight into God’s creation, and by the perverted state of nature itself, which made it more difficult to read nature’s purpose therein. Thus, man often errs in his grasp of the natural law, not to mention his will to live in accord with it even when it was grasped.
c) The moral law which God revealed to his people in the Old Testament was a more lucid restatement of the natural law, specified as was appropriate for the understanding of God’s people at that point in history, yet pointing beyond itself to a fuller revelation yet to come of creation’s end and how to live in accord with it.
4. Christ is the fulfilment of the law
a) When Christ came, he came as the objective revelation not only of who God was, but of what man was, and what man was intended to be. Through his life and death, through his teaching while on earth, and through the teaching of the Holy Spirit in his followers, He revealed the true end of creation, and how to live in accord with that end. That is to say, in his revelation of how men were to live with God, with one another, and with the world (which we could call the “evangelical law”) he revealed the true purpose and structure of the natural law as it applied to humanity in its full maturity.
b) This revelation superseded both the revelation given in creation and discernible in nature, and the revelation given in the Old Testament, not only because it was more direct, but also because it was a revelation of the nature of creation in its full maturity--it was a revelation of the endpoint of history in the middle. By superseding, it did not overturn or contradict what came before, but rather fully corresponded to that ideal of which the earlier revelations were necessarily incomplete approximations.
c) Although the revelation in Christ is thus the objective revelation of the true natural law, it is still limited in its subjective apprehension. This is true quite obviously because of the limits of our knowledge--we cannot understand Christ’s revelation either in its full clarity, since we see only through a glass darkly, or in its full extent, because of our finitude. The long practice of the Church in study and godly living, guided by the Spirit, can help us to grasp the revelation of God in Christ, as well as that in creation, better, but never completely. More importantly, we are limited in our ability to comprehend, receive, and live out the evangelical law, because we have only tasted of the fruits of the new creation, and still live partly in the old; we are thus still immature where Christ is the fully mature man, and can only receive and live out his revelation to the extent possible in our immature state and the immature state of the world itself. Again, the sanctification of God’s people through history will lead to a fuller, but never perfect, understanding and practice of the imitation of Christ, until at the consummation, we are perfected in him and attain to the full stature of creation.