All doctrine had to be either explicit in Scripture or a necessary consequence of reasoning from the Scriptures. They were not rejecting or devaluing, however, all previous thinking. Indeed the Reformers recognized there were those who went before them to whom God had given much wisdom. They had a sense of humility as they approached the Scriptures to ascertain what was the true Biblical teaching. But, one thing was certain, no matter who held to a given interpretation or doctrine, it had to be proven by the text itself.
Scripture is self-sufficient.
Scripture interprets itself. By comparing Scripture to Scripture, by going from what is most clear and basic and then progressing to more difficult passages, one can arrive at theological truth. We greatly need a renewed understanding of this principle today in Jewish ministry. First, most obviously, no matter what the great sages of Christianity and Judaism have said, a teaching must be derived solely from Scripture. We cannot ultimately depend on the traditions of Catholicism, the teachings of the Mishnah and Talmud, or even the beliefs of the Reformers themselves to come to truth.