One thing that is strange about the debate over free will between Erasmus and Luther is that they are arguing on two very different levels. Erasmus is the voice of common sense — “if we don’t have free will, then how can we be morally judged?” — whereas Luther takes the apparently loony position that we both lack free will and stand under the most severe possible judgment.
I think one way to understand the shift in perspective is not the term “will,” which I don’t believe Luther denies to human beings, but rather the term “free.” Erasmus means “free” in the straightfoward sense of unconstrained or autonomous, whereas Luther means “free” as opposed to “enslaved.” And in that sense, there can be no “free will” — every human being is enslaved to Satan until God rescues him and restores him to his rightful status as a slave of God. The problem isn’t the specific things we do with our wills, but rather the fact that we will as though we were “free” in the sense of being autonomous alongside God. The problem is that we presume to believe that God needs our go-ahead for salvation, which is tantamount to saying that God should obey our will in the matter of salvation. But that’s not how it works: we’re God’s slaves, and so anything we do that claims autonomy or anything like “rights,” anything we do on the assumption that we have been freed from the divine service, is sin.
Interestingly, Erasmus is the one who introduces the image of a slave, asking whether a just master would punish a slave for something he can’t help. This imagery is kind of strange in a culture where there hadn’t been slavery (at least by that name) for centuries, and presumably it comes from the New Testament and the Greek literature that Erasmus is steeped in. Luther turns around and takes this literally — if we are slaves, which the New Testament says absolutely constantly, then we have no claim on our master. You don’t morally exhort a slave, you give orders. The good slave isn’t one who has refined his will through moral striving, but the one who sets aside his will entirely and obeys.
There’s a lot to say about the fact that a more radical and literal theological concept of slavery asserts itself just as European culture is set to readopt slavery on the largest possible scale. For the moment, I will content myself to make an observation about Agamben’s recent study of slavery in The Use of Bodies. He claims to be discovering some new potential in Aristotle’s figure of the slave, but Christianity already made all human beings into slaves — and I would even say that for Luther, we are slaves in precisely the Politics Book 1 sense. Agamben uses the study of slavery to claim that we need to rediscover the realm of use, but Christianity had already made “use” the guiding concept — not only in Paul (where we are to make use of our social status), but most spectacularly and systematically in Augustine (where we make use of the faux-peace of the earthly city to spread the gospel).
In short, I wonder if Agamben is laboriously rediscovering Christianity.