Which is what St. Cyprian would probably say if he were sitting on a North American Presbyterian study committee. There are many varieties and interpretations of Calvin–indeed, many Calvinism(s). Indeed, my friend at EvangelicalCalvinist–his work on T.F. Torrance–has completely destroyed the soteriological structure of the Westminster Confession of Faith, and I commend him for it.
On the other hand, as the recent controversy on the Federal Vision demonstrated in Presbyterian circles, it really doesn’t matter what these Calvinisms say, and quite frankly it doesn’t even matter what Calvin said. The only thing that matters is The Westminster Confession of Faith. Unfortunately, that is not good enough, since the original Confession is fairly theocratic–libertarians in California opted out for modifying it. Therefore, the next conclusion: the only thing that matters is how the Westminster Confession of Faith is interpreted by specific Reformed synods.
But what of those who are not part of a synodal Reformed body? In large part they are free to do whatever they want. Secondly, they have the advantage of being allowed to jettison aspects of Westminster Federalism that are clearly faulty. Their main drawback, though, is that independent churches usually don’t have a long shelf-life. They are often birthed in schism and if they don’t schism later on, they usually dwindle over a generation or two.
Another more serious problem, though, is that neither group can seriously pretend to have the faith once delivered to all the saints for the simple reason if new truth and doctrine break out, then by definition it can’t be part of the faith once delivered to all the saints.