False teacher Peter Leithart offers a helpful summary of why proponents of the Federal Vision believe in monocovenantalism (the belief that the pre-fall Adamic Covenant was essentially the same as the post-fall Covenant of Grace).
Grace and law from God’s side, and a demand for faith and obedience from man, characterize every covenant in Scripture. No covenant is exclusively legal or exclusively gracious. No one is ever called to a dis-obedient faith or a faithless obedience.
Read the rest to understand this influential error. See also Doug Wilson’s CREC “Examination” Questions 5, 8, 39-46. Compare with John Murray’s rejection of a works principle anywhere in Scripture.