⭐ The turning point in method on this thread: here Luther moved the question is the will free? out of metaphysics and judged it instead as a question about the cross.
The issue
Is the way to know God the way of his evident power and glory, or the way of the weakness and suffering of the cross?
Claim
Luther's theology of the cross: God reveals himself, as Olson puts it, through weakness, suffering and bearing the sins of the world, and to the natural mind this is an offense and a stumbling block. On this basis he concluded, in Olson's words, that believing human free will has a part in salvation is an example of the theology of glory — one more proof of human pride stubbornly fighting the cross that declares humanity weak and helpless. ⭐ The key is the order: he did not first argue that the will is bound and then turn to the cross; he looked first at the cross, and from it concluded that the will is bound.
Counterclaim
The theologians of late medieval scholasticism, Olson notes, with very few exceptions, accepted the freedom of the will as part of their synergistic doctrine of salvation. ⚠ The material for this field is thin; see the editor's note.
⚠ Readers please note: this field is thin, and abnormally so. Our base text gives the opposing side only a one-sentence summary here, with no particular person and no particular words. Our practice is not to write on their behalf — what you see here is not the opposing side's full case, only the opposing side as Luther wrote about it. ⭐ If you want to hear this side speak in full, read on to the exchange six years later: Erasmus's On Free Will of 1524 — that was the first time this side had the chance to answer Luther in its own words, at length.
Aftermath
⚠ The timing, as Olson gives it: less than a year after the Ninety-five Theses were posted in Wittenberg, Luther was invited to the Augustinian monastery in Heidelberg to explain his program of reform, and he decided, Olson writes, to go straight to the heart of his difference from scholasticism. ⭐ Olson's judgment on the weight of this step: everything else in Luther's theological contribution, he says, starts from here and keeps coming back here. Six years later it was exactly this core that Erasmus chose to debate him on.