But conversely, he would say that everybody in heaven is in heaven solely because of faith. So there are only those with faith and those without faith, and this is the determining criteria in who is among the blessed and who is among the damned.
This is tricky, because there is a Catholic way we could understand this. Certainly nobody who does go to heaven does so without faith, and people in hell can be said to have been lost through a lack of faith. Yet this is not the case because faith alone in and of itself is intrinsically sufficient to effect justification in us - it is but one element in a series of things that lead to heaven, mainly in the sense that the virtue of faith, besides being pleasing to God, disposes us to receive the actual graces God wants to shower upon us so that we can be rendered fit for heaven.
This got me thinking about grace and faith in Protestantism, and how among many Protestants, faith actually serves the same role that grace does in Catholic theology. For Catholics, grace is the very righteousness of God, according to the Council of Trent, "God's justice, not by which He Himself is just but by which He makes us just" (D 799). St. Paul likens grace to the very charity of God given to the elect: "The charity of God is poured forth in our heart by the Holy Ghost" (Rom. 5:5). Sanctifying grace is truly distinct from charity, though the Council of Trent spoke of grace in terms of charity (D 800).
Like charity to which it is so closely connected, grace is a vivifying principle, something that renders one acceptable to God and empowers one to conform themselves to the image of Christ. Without grace, nothing we do can have merit, and all the good we do comes as a result of God's grace in us, either actual or antecedent to whatever good we perform.
If we think about this, we see that this is the role assigned to faith in classical Protestantism. If we examine Luther's Larger Catechism we see faith identified as the vivifying principle in salvation:
Article IV of the Augsburg Confession states:
...men cannot be justified before God by their own strength, merits, or works, but are freely justified for Christ's sake, through faith, when they believe that they are received into favor, and that their sins are forgiven for Christ's sake, who, by His death, has made satisfaction for our sins. This faith God imputes for righteousness in His sight.
Notice that in Catholicism, grace is defined as the righteousness of God communicated to man which in turn makes Him righteous and holy. This is almost exactly what Protestants believe concerning faith. Protestants today use the same language: works must be done "in faith" in order to be acceptable to God (and even then they don't have any intrinsic merit); trusting in anything other than faith alone is tantamount to arrogant idolatry, just as in Catholic it would be in Catholic theology to assert that man can merit without grace; faith is what is sought to get one through difficult trials and periods of darkness, just as we would implore God's grace; Protestants believe we are saved by "faith alone" and Catholics say the same thing about grace. In most aspects of Protestantism, faith is seen the way we view grace.
Though faith plays the same role in Luther's theology that grace does in Catholic theology, there is a still greater difference. Grace is something external, objective and transformative. Faith, at least the kind Luther espoused, was internal, subjective and ultimately served only to give the sinner "imputed" righteousness.
With all the tremendous emphasis on faith in Protestantism, both classic and modern, it would be interesting to see what role they assign grace in the life of the Christian. If faith is the operative element that accomplishes everything, strengthens the believer and makes his prayers and deeds meritorious, indeed even rendering us justified, what is there left for grace to do?