One of the things that quickly dawned on me as I explored this idea is that there isn’t really one concept called Sola Scriptura. Rather, there are a variety of different perspectives, often flowing from different times and places, that all operate under that general umbrella.
Luther, for example, had little patience with the idea that every single person could somehow rightly interpret scripture for himself. He primarily used the idea to assert his interpretation of the Holy Scriptures over against the Roman Catholic magisterium’s interpretation. That was really true of all the primary reformers who used the power of their respective states to enforce their interpretation and defend against Rome. They largely viewed themselves, to the extent I can tell, as rescuing the tradition of interpretation from the “corruption” of the Roman Catholic magisterium. Again, as far as I can tell, they perceived their interpretation to be informed and continuing the tradition of the Church.
The radical reformation and then revivalist movements added different takes to the concept. It became common to assert that all truth or belief and practice was found in the Bible. This took two sorts of forms. On the one hand, some held that anything done or practiced that was not found explicitly in the text was, as long as it did not contradict the text, something allowable that a person or community might choose to do if they desired. Others held the harder perspective that if it wasn’t found in the Bible, that meant it was prohibited.
Many pietists came to believe that using nothing but a Bible, without any context, cultural setting, or reference to any traditional interpretation, any individual believer would be led into the truth by the Holy Spirit. This sort of view became particularly prevalent as individualism began to be deeply intertwined with the threads of modernity.
Others interpret Sola Scriptura to mean Prima Scriptura. That is they look to Scripture for what they interpret it to say about a topic first, recognizing that many forces and sources influence our understanding, belief, and practice. To some extent, this is a chastened view of Sola Scriptura. In practice, though, each individual still makes the decision what to consider or not consider along with the Bible.
I’m sure in my summary I’ve mischaracterized some of the perspectives on what sola scriptura means and how it is practiced. Some of them are difficult for me to wrap my head around. They feel like very odd ways to view reality. But the core idea is that sola scriptura itself has no single meaning. Rather, there are a variety of perspectives, some very different from others, that fit under this particular concept.