The two covenant scheme of the Westminster Standards has been absolutely essential in combatting the Neonomianism of both Norman Shepherd and the Federal Vision, not to mention Roman Catholicism. There are, of course, matters in which the two covenants are similar (they are both covenants sovereignly administered by God, for instance). But the nature of these covenants and the way of salvation offered in them must be clearly and consistently contrasted if we are to avoid arriving at a doctrine of salvation that is markedly in contrast with our Standards and which therefore is something other than Reformed (not to mention biblical).

—Rick Phillips, “Grace, The Two Covenants, and Merit”