And where in the Bible is this information provided?
I don't see how what Bible one does or does not use is an issue here; in fact I was trying to eliminate that aspect of it altogether - so to make my point I used the Douay-Rheims, which is what I thought Roman Catholics use. Am I incorrect?
But to answer your question, if you mean in the context of 2 Timothy 3:16-17, I think it's safe to say that Paul was referring directly to the scriptures that he and his new congregations had, which was, first and foremost, the Jewish Tanakh, or Old Testament. In addition, since the letters to Timothy were probaby written after most of the epistles and gospels, I guess it's safe to say that many of those letters were in circulation as well, although of course not nearly as much so as the officially established scriptures of the OT.
My own personal opinion is that because all scripture is given by divine inspiration and God exists outside of time and knows the end from the beginning, He of course knew exactly what books would end up in the canon and as a result, those verses are meant for future Christians to understand as meaning the entire canon of scripture. Aha! you say, but it was the Roman Church that established the canon. :) Of course they did, and do I believe they were led by God? Absolutely.
So what exactly are we disagreeing about here? :) My only problem with tradition being taught and practiced in addition to scripture is if it is contrary to scripture. Surely Catholics and non-Catholics can agree upon that point.