The symmetrical biographies of John Henry Newman and John Nelson Darby sum up the problem of modern historical Protestantism groping for a solid foundational ground.
My opinion is that there is none -- neither institutional continuity, nor creed, nor scripture, nor experience are beyond valid criticism -- and ironically the endless struggle of the alternative "foundations" have helped in making that clear to all.
But -- still imo -- the very principle of "faith" is the opposite of the search for foundation (fundamentalism in the etymological sense). It is walking on the sea, not on solid ground.