Some historians have characterized the struggle between Martin Luther and Pope Leo X as a struggle between "Papal Authority" and "Individual Experience / Revelation".
The same conflict can be described in a different way: "Is the ultimate source of authority in the Pope or in the Text?" Behind the different wordings lie two different notions of what Luther was really doing.
For the Roman Catholic Church in the 1500's, the Pope was the final word: what he said, was to be considered as the final decree on any topic.
For Martin Luther, the Text (i.e., the Hebrew and Greek documents which we call "Tanakh" and "New Testament") was the final word. Since we can all (hopefully!) read, we can each individually have access to the text for ourselves. It is in this sense that Luther stressed "individual experience."
Luther is sometimes mis-understood in this matter of "individual experience" - he was not a mystic, although there were many mystics in Luther's time. Luther did not want to place too much emphasis on individual spiritual experiences or revelations, because they retain a mainly subjective element. Rather, Luther located authority in text, because this made it objective. The letters on the page are the same, no matter who reads them! Certainly, there will remain a certain amount of subjectivity, as each person reads a text slightly differently. But the essence of text is objective, and that is what Luther was looking for.
The subjective side of Luther, then, lies in the fact that he empowers each individual to study the text and draw meaning from it; and as different individuals examine the same text, different interpretations will arise.
The objective side of Luther is seen in the fact that he views the text as the location of truth, publicly accessible to all; the ink on the page does not change, even if the readers do. The text is an objective fact.
So is Luther an objectivist or a subjectivist? Or both?