In scholastic theological discourse, 'moral suasion' and 'physical influence' represent two different ways of getting someone to do something. If my goal were, say, getting my four-year-old daughter to the dinner table, I might employ 'moral suasion' by promising her that she'd find her favorite dish when she arrived there, or by simply threatening her with consequences for refusing to follow my instructions to cease and desist from playing and join us for supper. I might, alternatively, employ 'physical influence' by simply picking her up, compliant or not, and carrying her to the table.
This distinction finds expression, among other places, in the Synod of Dort's explanation for how God brings his elect to faith and repentance. "God," the Canons of Dort argue, "not only sees to it that the gospel is proclaimed to [the elect] outwardly, ... [but] also penetrates into the inmost being, opens the closed heart, softens the hard heart, and circumcises the heart that is uncircumcised. God infuses new qualities into the will, making the dead will alive, the evil one good, the unwilling one willing, and the stubborn one compliant."
The Divines at Dort described God's act of 'physical influence' upon the will in such terms to counter semi-Pelagians who professed that divine grace precedes every positive movement of the human will towards salvation, but -- when pressed -- were forced to admit that by 'grace' all they really meant was God inviting, threatening, pleading with, and otherwise attempting to suade [sic] sinners to embrace the Gospel. The underlying assumption of such persons was that sinners retain sufficient freedom of the will to respond positively to the Gospel when it is properly set before them. Grace in such a semi-Pelagian scheme need not entail any actual influence upon the will, and -- correspondingly -- remains something which can be resisted by those whom it confronts.
Though Luther never employs the exact terms I've outlined above ('moral suasion' vs. 'physical influence'), I believe this distinction lies at the heart of the difference he posits, in his Bondage of the Will, between God's work of regenerating those whom ultimately believe and God's work of hardening those whom ultimately perish in unbelief.
So enslaved, in Luther's perspective, is every human person's will to that human person's sinful nature -- i.e., so enslaved is every person's will to sin (cf. John 8.34) -- that Luther, though admitting that people sin freely and under no compulsion, is reluctant to attribute 'free choice' to sinners at all. For sinners to exercise faith in Christ, then, requires a divine act of physical influence upon their wills. "The ungodly does not come even when he hears the Word [moral suasion], unless the Father draws and teaches him inwardly [physical influence], which He does by pouring out the Spirit. There is then another 'drawing' [namely, one of physical influence] than the one that takes place outwardly [i.e., that of moral suasion]; for then" -- that is, when God employs his Spirit to bring someone to faith -- "Christ is [so] set forth... that a man is rapt away to Christ with the sweetest rapture, and rather yields passively to God's speaking, teaching, and drawing than seeks and runs himself."
For Luther, as for the Divines at Dort, 'moral suasion' and 'physical influence' coincide in the work of regeneration -- "it has thus pleased God to impart the Spirit, not without the Word, but through the Word" -- but the latter is utterly indispensable to any right response to the Gospel. Elsewhere Luther describes this "inward" work of God upon the will thus: "If God works in us, the will is changed, and being gently breathed upon by the Spirit of God, it again wills and acts from pure willingness and inclination and of its own accord, ... willing and delighting in and loving the good just as before it willed and delighted in and loved evil."
But Luther employs decidedly different language when he discusses God's hardening of Pharaoh's heart (and the hearts of all who die in final unbelief) in Exodus 9:12 (cf. Romans 9:17-18): "[God] provoked [Pharaoh] and increased the hardness and stubbornness of his heart by thrusting at him through the word of Moses, who threatened to take away his kingdom and withdraw the people from his tyranny, without giving him the Spirit inwardly but permitting his ungodly corrupt nature under the rule of Satan to catch fire, flare up, rage, and run riot with a kind of contemptuous self-confidence."
In other words, God hardened Pharaoh's heart through an act of 'moral suasion' alone. God confronted Pharaoh with a word which required Pharaoh to give up something he held dear, and in so doing provoked Pharaoh to cling more tightly to that very thing. Luther again explains: "It is thus [God] hardens Pharaoh, when he presents to his ungodly and evil will a word... which that will hates -- owing of course to its inborn defect and natural corruption. And since God does not change it inwardly by his Spirit, but keeps on presenting and obtruding his words... from without, ... the result is that Pharaoh is puffed up and exalted by his own imagined greatness, ... and is thus hardened and then more and more provoked and exasperated the more Moses presses and threatens him."
Thus God "hardens" all who are exposed to the Word without a corresponding work of God's Spirit to bring them to faith and repentance: "This provocation of the ungodly, when God says or does to them the opposite of what they wish, is itself their hardening or worsening. For not only are they in themselves averse through the very corruption of their nature, but they become all the more averse and are made much worse when their aversion is resisted or thwarted." In Luther's judgment the Gospel proves the ultimate "provocation of the ungodly," because it calls sinners to abandon their most prized possession -- their own self-righteousness.
This basic difference between God's act of hardening (through 'moral suasion') and God's act of softening (through 'moral suasion' and 'physical influence') human hearts should be carefully noted. It reminds us, among other things, that God is not the author of corrupt nature or sinful human acts as such. If, in fact, God hardened human hearts in some way analogous to how he softens them -- by an act of physical influence upon them -- Scripture's claim that God is "too pure" even to "look upon sin" (much less to be the culpable cause of sin) might seem to ring hollow. Persons who, like the Divines at Dort, accept with Luther the biblical truth that God has in fact predestined some (undeserving) sinners to eternal life (accomplishing their salvation in time) and predestined other (deserving) sinners to eternal death (accomplishing, in a fundamentally different way, there condemnation in time) would do well to articulate the difference in how God ultimately achieves those respective ends with as much precision and care as Luther.
Aaron Clay Denlinger is professor of church history and historical theology at Reformation Bible College in Sanford, Florida.