Enough, as we have been saying, ought to be enough. We've heard the crucial sentence from Article VII of the Augsburg Confession over and over these days, about what's enough for the true unity of the church, namely the one and only gospel proclaimed and enacted in the assembly of believers. We have to suppose that the confessors that sunner day in 1530 meant precisely what they said about preserving and maintaining the genuine unity of the church-enough to have some prima facie acknowledgment that it is indeed the Christian gospel being said and done in this and that assembly of the faithful. Not that gospel plus some theological proposition or some canonical requirement, we'd want to say. For we've learned the lesson well: gospel plus anything is always less than gospel.
Truemper, David G., "Enough, Already-But Perhaps Not Yet: Liturgy, Church Unity, and Eschatology" (2003). Institute of Liturgical Studies Occasional Papers. 100.