As David Hart observed recently, Romans 5:18 is a verse with hard-to-avoid universalist implications: “ἄρα οὖν ὡς δι’ ἑνὸς παραπτώματος εἰς πάντας ἀνθρώπους εἰς κατάκριμα οὕτως καὶ δι’ ἑνὸς δικαιώματος εἰς πάντας ἀνθρώπους εἰς δικαίωσιν ζωῆς.” (“Therefore as by the offence of one judgment came [cf. Rom 5:16] upon all men to condemnation; even so by the righteousness of one the free gift came [cf. Rom 5:16] upon all men unto justification of life.”) Augustinians (including Thomists and Calvinists) tend to seize on the universalism of the first clause — original sin is a calamity that afflicts all of humanity, molding us into a single massa peccati. And that strikes me as a fair reading of that clause.
The only problem for Augustinians (of any stripe) is that the second clause endorses an equal but opposite universalism: just as surely as condemnation came to all because of sin, so too the “justification of life” is for “all men.” Not some, but all. It seems that we can only avoid the passage’s universalism by interpreting the sense of “all” equivocally in the two clauses; but is that even grammatically defensible?
This is an interesting problem.