A Question

Here is a question I've really been wrestling with lately: Given that the writers of the epistles/letters were not intending to write Scripture (they all considered "scripture" to be the Tanakh/Old Testament, among other writings), can we equate their words with the words of the Tanakh? Put another way - can anything (literally, anything) that is written or said in the New Testament be understood independent from the Tanakh? To put an even finer point on it, if someone is espousing a theological idea that they have taken from the New Testament, but that idea doesn't have some kind of root in the Old Testament, could that idea have even possibly existed in the minds of the writers of the New Testament?

I guess what's really bothering me lately is when I hear some teaching about something Paul wrote, or something James wrote, and the speaker then draws some conclusion that couldn't possibly have been the case because it would require a completely different understanding than the person writing it could have possibly had. Take 'election' for example, because in my opinion this is one of the most poisonous Christian doctrines out there. Election, in OT terms, is meant to refer to Israel. Always. There are no exceptions. So when Paul talks about election, he's talking about Israel - or at the very least, he is using the metaphor of God's election of Israel (to special service and calling) to illustrate that it is God who saves someone, or gives someone a special role, not the other way around. In other words, the entire idea of election in the NT cannot be new. Paul is in the midst of a conversation that is already on-going, addressing a people who are likely familiar with the Tanakh, and is using ideas that would have been familiar and understandable to his audience. It is our job to figure out what the conversation is, who he's addressing, and what ideas he's drawing on in order to say what he says. So often though, the work is skipped over, and the applications are made sloppily. As Gentile disciples, we have to do the work.