It is one thing to argue for a covenantal perspective on election, justification, and sanctification — perhaps even other loci in dogmatics. However, are we expecting too much of a biblical-theological motif by suggesting that it generates its own ontological framework? ... [Micheal S. Horton, Covenant and Salvation: Union with Christ (Louisville, KY: WJKP, 2007), 182]
Nevertheless, this union that we enjoy is effected for and in us not by an impersonal process of emanations, by a ladder of participation, or by infused habits but by the Holy Spirit, who gives the ungodly the faith both to cling to Christ for justification and to be united to Christ for communion in his eschatological life. Mediation is not a principle or a process, but is located in a person. .... (p. 183)
In none of the New Testament contexts (including 2 Pet. 1:4) does koinonia (or its cognates) "refer to a mystical fusion with Christ and God, but to fellowship in faith." (p. 185)
As a result, the New Testament writers refer not to a general participation in being but to union with Christ as the locus of our redemption. ... (p. 186)
It is not as if Paul has no ontology; for him "the ethical is itself ontological," which requires a "covenant ontology." ... (p. 204)
One of the electives that I had audited in WSCAL dealt with the topic of 20th century Roman Catholicism, a topic which was truly mystifying. I had wondered then, and still do wonder, why there is such a need to reinvent ontology, as it were. Supposedly, the problems with the modern world came about because of extreme voluntarism and a rejection of a realistic Platonic ontology, where earthly things participate in heavenly realities. Thus disconnected, the modern secular world had arisen whereby God and the divine is pushed to the periphery of societal thought, or even rejected altogether.
The ontological project within the Nouvelle Theologie and Radical Orthodoxy points towards the idea of ontological participation as methexis. Under this scheme, the (particular) earthly thing participates in the (universal) heavenly form. The ontological participation is univocal, in the sense that there is a quantifiable difference and not qualifiable difference between the particular and the universal. As an example, the church participates in Christ's body such that it can be said that the church in its essence is always spiritual, holy and sinless just as Christ is spiritual, holy and sinless. That is one of the many reasons why Rome can never said that she has ever erred, for as Christ is sinless, so His body must be sinless. Individual priests may err, but the Church as a whole cannot err.
That modern society is essentially godless is true, but why is a flawed ontology the cause of such godlessness and wickedness? For children of the Reformation, we know Man's problem is sin and rebellion against God, which is an ethical not an ontological problem. Both Micheal Horton and Neo-Orthodox theologian Bruce McComarck agreed with that analysis. Yet, Dr. Horton attempts to come up with what he calls a "covenant ontology." But if we all agree that the problem with humanity and its alienation from God is ethical, not ontological, why do we even need to have this category called "covenant ontology" at all?
Horton calls for participation in the sense of koinonia, a Greek term often translated as "fellowship." Neoplatonist ontology speaks of ontological participation as methexis, while Christian participation is one of koinonia, and thus a sharing of life one with another. According to Horton, it is explicitly not a mingling of essences, but a communion from the divine energies. Thus, this idea of participation as koinonia is his version of "covenant ontology" which underlies the doctrine of Union with Christ.
Koinonia is indeed what Christians are called to. We are indeed called to have fellowship with God and each other. Yet, I do not see why koinonia is to be part of any supposed "covenant ontology." The idea of koinonia is ethical, not ontological. When I have fellowship with a Christian brother over a meal, there is no ontological "mingling" or change of my essence and his essence (whatever that is supposed to mean). Nothing happens ontologically when fellowship between Christians happen, unless one party decides to take a knife to the other party (for example).
I understand that koinonia is indeed the Christian answer to methexis, for our salvation lies in our union with Christ rather than any participation in ultimate being. But it is also for this reason that the answer is to reject ontology as the realm to seek out the answers to questions on salvation, and instead put forward ethics as the realm we should go to. If one wants to speak about Christian metaphysics, I think a clear case can be made for that from the doctrine of creation and the portion of the doctrine of the Fall that relates to creation (namely the curse upon the earth), without recourse to redemption. Creation is creation; redemption is redemption, and the two should not mix with each other.