It is objected by Roman Catholics and Eastern Orthodox that there is no verse that teaches sola scriptura. But I tend to disagree with this assessment because I believe that 1 Corinthians 4:6 teaches sola scriptura. But suppose I am all wrong about that and it in fact does not teach sola scriptura, does this entail that I should be a Roman Catholic or an Eastern Orthodox? In other words: What are the implications if one rejects that sola scriptura is taught in the Bible? My contention is that there is really no major implication to Protestantism if scripture alone is not taught in the Bible.
So let us suppose for the moment that sola scriptura is not taught in the Bible and that we reject the Eastern Orthodox and the Roman Catholic arguments (as I have done elsewhere on this blog) then all we are left with is scripture. So we could modify our view of God's revelation to be as follows: Scripture alone is the only infallible and authoritative rule for faith and practice that we have knowledge of. As for there being additional revelation other than the Bible we should withhold belief that such additional revelation exists. In other words, with respect to the proposition that there is additional revelation other than the Bible we should be agnostic with respect to this proposition.
Once one has accepted this epistemological form of sola scriptura (the criteria given above) then it seems like the Roman Catholic and Eastern Orthodox claims of incoherence lose their weight. This is because the conjunction of reason and scripture warrant the conclusion that these are the only scriptures we know of (this is of course assuming that the other church authority arguments fails). Therefore, there is no logical incoherence with this epistemological version of sola scriptura.
Conclusion
So even if Protestants cannot provide a proof text for sola scriptura this still does not entail that one should be a Roman Catholic or Eastern Orthodox. In fact it would appear that the epistemic status of Protestantism is not effected at all if one cannot give a proof text.
Additional arguments must be given and have dealt with those arguments in the posts referenced below.
For the refutation of all the positive arguments that the East and Rome gives for believing their positions see the following blog posts:
Canon Argument:
http://reasonfromscripture.blogspot.com/2009/08/refutation-of-canon-argument.html
Perspicuity:
http://reasonfromscripture.blogspot.com/2009/08/refutation-of-roman-catholic-and.html
Infallible Interpretations:
http://reasonfromscripture.blogspot.com/2009/08/do-we-need-infallible-interpretation-of.html
Scripture Alone:
http://reasonfromscripture.blogspot.com/2009/02/sola-scriptura.html