Theonomy (theo – God, nomos – law, meaning God’s law).
Historically the Christian movement has been beset by two significant heresies: Marcionism and Antinomianism.
Around AD 144 Marcion dualistically represented the God of the Old Testament as a vengeful tyrant, while the superior God of the New Testament was one of love and forgiveness—and never shall the two meet. This heresy is alive and well as many Christians buy into the false antithesis between Old and New Testament as one of law and grace. It is not biblical Christianity and leads to antinomianism—a gospel of grace to the exclusion of objective ethical requirements, thus opening the way to a rejection of God’s universal moral law revealed in the Ten Commandments. And yet, Jesus declared, “If you love me, you will keep my commandments” (Jn 14:15; also 15:10), and Paul likewise declared that “love is the fulfilling of the law” (Rom 13:10b; see also 1 Jn 2:3-6; 5:3; 2 Jn 6; 1 Pet 2:21). Clearly love and law-keeping are not antithetical. Nonetheless, our obedience is now supernaturally enabled, because the
Law of the spirit of life in Christ Jesus has set you free from the law of sin and death.
Through the Gospel both law and grace are in harmony: the law – in summary and specifics – is written on our heart (Rom 2:14-15; 2 Cor 3:3; Heb 8:10). It exposes and defines our sins, judicially condemning us to death. Consequently Christ had to show himself as both “just and justifier of those who believe” (Rom 3:26); that is, he could not arbitrarily forgive, there had to be justice and thus propitiation for sin. Hence, Christ died vicariously – in our stead – for him to be both “just (i.e. law) and the justifier (i.e. grace)”. Consequently, without the continuity of God’s law into the New Testament, the Gospel is made a nonsense.
Theonomy not only demonstrates the harmony of OT and NT – of Law and Gospel – but it validates the ethical force of the OT law in all its specifics as a divinely revealed objective standard for the sanctification (ethical holiness) of the believer and for social justice.