There can be scripture without revelation. For revelation always and only becomes a reality where there is faith. The unbeliever remains under the veil of which Paul speaks in 2 Corinthians 36. He can read scripture and know what it contains. He can even understand, purely conceptually, what is meant and how its statements cohere, yet he has no share in the revelation. Revelation is in fact fully present only when, in addition to the material statements which testify to it, its own inner reality is itself operative in the form of faith. Consequently revelation to some degree includes its recipient, without whom it does not exist. Revelation cannot be pocketed like a book one carries around. It is a living reality which calls for the living man as the location of its presence.
In view of what has been said, we may, therefore, affirm that revelation goes beyond the fact of scripture in two respects: as a reality deriving from God it always extends upwards into God’s action; as a reality which makes itself known to man in faith, it also extends beyond the fact of scripture which serves to mediate it.
This non-coincidence of scripture and revelation makes it clear that quite apart from the question whether scripture is the sole material source or not, there can never really, properly speaking, be a sola scriptura in regard to Christianity. As we have already said, that was still clear in principle to the great Reformers, and only fell into oblivion in what has been called Protestant orthodoxy. Scripture is not revelation but at most only a part of the latter’s greater reality.- from Revelation and Tradition (with Karl Rahner, 1965)