Herman Bavinck sees the covenant of grace through the eyes of covenant. This is redundant, but necessarily so. Bavinck knows reformed theologians have wrongly understood the covenant of grace through the lens of the doctrine of divine decrees and have therefore abandoned the idea of conditionality in the covenant.
He writes, "In the beginning Reformed theologians spoke freely of 'the conditions' of the covenant. But after the nature of the covenant of grace had been more carefully considered and had to be defended against Catholics, Lutherans, and Remonstrants, many of them took exception to the term and avoided it," (Reformed Dogmatics, vol 2. p.229). Conditionality wreaks of Arminianism to boot.
Bavinck affirms both the unilateral and bilateral nature of the covenant. He does this because understanding this concept of covenant according to a perspective of election makes for an impossibility. That is because, in this scenario, the covenant can only be seen as unilateral: God supplies humans with everything they need for salvation on the one hand, but humans are automatons on the other. Contrarily, a bilateral covenant is an impossibility from an electionist perspective: humans cannot will to power (Nietzsche) their salvation due to their finitude and original sin. Therefore, a hermeneutic starting with the doctrine of election and deducing doctrine (loci) from the pages of Scripture makes understanding the whole of Scripture a difficult task; so much so that the doctrine of election becomes a double edged sword wielding its way through the Bible declaring what can and cannot be e.g. warning passages written to the elect (the elect cannot fall, therefore a warning to them is meaningless and only plays existential or subjective tricks upon them--which of course God would not do).
Of course, Bavinck declares that in the covenant of grace, God supplies humans with everything they need for salvation in Christ. This, he says, is the unilateral aspect of the covenant. Moreover, in order to rescue humans from being automatons, he gives the covenant its existential import in the bilateral aspect of the covenant: it has flesh and bone and moves through history, it moves through households, it is organic and appeals to the whole man: his money, possessions, his wife and children his house and talents.
"The covenant of grace, accordingly, is indeed unilateral: it proceeds from God; he has designed and defined it. He maintains and implements it....But it is destined to become bilateral, to be consciously and voluntarily accepted and kept by humans in the power of God," (ibid, 230 emphasis mine).
The covenant of grace is rightly called a covenant of "grace," because in its unilateral aspect, the Lord God provides all the benefits sinners need in order to be justified and sanctified in Christ Jesus through his death and resurrection and by the subsequent power of the Holy Spirit. It in its bilateral aspect, the covenant is "kept by humans in the power of God." Human will is regenerated and (definitively) sanctified by the power of God (unilateral aspect), and also, humans bare responsibility to obey the commands of the Lord, and they do so only by means of his grace (bilateral aspect). The following Scriptures from the Apostle Paul reveal this theme: "May God himself, the God of peace, sanctify you through and through. May your whole spirit, soul and body be kept blameless at the coming of our Lord Jesus Christ (1 Thess. 5:23)," and "I have fought the good fight, I have finished the race, I have kept the faith," (2 Tim. 4:7).
Discussing the nature of the human will as it relates to or works with the Lord's will is a topic for another day, nevertheless--the covenant of grace has both aspects of unilateral and bilateral nuance and the Bible favors this view.
What about unbelievers in the covenant? Surely, we have all looked askance at the nonplussed individual, slouched in his chair, mulling over his venti mocha, hair disheveled, legs spread out. What about that guy? Reformed theologians have tried to answer this question by means of drawing distinctions in the covenant, making two out of one: internal/external, a covenant vs. a covenant administration, an absolute and a conditional covenant--all of these pairs subsumed under the auspices of one covenant of grace.
Bavinck rightly rejects any type of bifurcation resulting in two covenants "under one" in attempting to explain away the reality of apostasy and/or unbelief within the covenant community. Rather,
"The covenant of grace is one, and the external and internal sides of it, though on earth they never fully coincide, may not be split apart and placed side by side. Certainly there are bad branches on the vine, and there is chaff among the wheat; and in a large house there are vessels of gold as well as vessels of earthenware (Matt. 3:12; 13:29; John 15:2; 2 Tim. 2:2o)," (p.232).
"But we do not have the right to separate the two [sides of the covenant]: in the day of harvest God himself will do this. As long as--in the judgment of love--they walk in the way of the covenant, they are to be regarded and treated as allies. Though not of the covenant, they are in the covenant and will someday be judged accordingly. Here on earth they are connected with the elect in all sorts of ways; and the elect themselves, since they are members of the Adamic race, can as an organism only be gathered into one under Christ as their head in the way of the covenant,"(p. 232).
Bavinck's solution here is to draw a distinction between being "of" the covenant and "in" the covenant, but he does not elaborate upon this point. This "of" versus "in" concept is worthy of discussion. How can someone be "in" covenant with God, but simultaneously not "of" his covenant? This seems like a scholastic solution. However, the strength of his argument is in his strict denial of bifurcating the covenant and holding to its unity, denoting two aspects of it in its unilateral and bilateral import. The weakness here is in boiling the huge problem of apostasy and unbelief down to the difference in meaning between two prepositions. There is this, however, from John's letter: "They went out from us, but they were not of us; for if they had been of us, they would have continued with us. But they went out, that it might become plain that they all are not of us," (1 John 2:19). This does not answer all of our questions regarding pagans in the pew, but it does give us a decent precedent for understanding the nature of the Christine life, church, justification and sanctification within the covenant community.
Our understanding of the covenant of grace as both unilateral and bilateral does justice to the nature, sovereignty and will of God in his saving humans, and it gives us great impetus to work out or salvation with fear and trembling, knowing also that our loving heavenly Father wills to work good in us. Let us have faith and trust and obey. For this is the way of the covenant.