You are probably remembering two connected passages, especially MacCulloch’s discussion of Luther on PDF pages 173–174.
What MacCulloch was saying
Luther was deeply influenced by Augustine’s view of salvation:
- humanity is radically corrupted by original sin;
- human beings cannot earn salvation through moral effort;
- salvation begins entirely with God’s grace;
- a person is justified—placed in a right relationship with God—through faith rather than meritorious works.
MacCulloch says Luther drew a sharp divide between salvation by works and salvation by faith alone. But Luther did not arrive at this doctrine by neutrally collecting every biblical passage and allowing them all equal weight. Instead, his Augustinian understanding of grace became the lens through which he interpreted Scripture. MacCulloch, PDF p. 173 (file not included in this release)
The crucial issue: Luther added “alone”
Romans 3:28 says, in substance:
A person is justified by faith apart from works of the law.
When Luther translated it into German, he added the word “alone”—faith alone—even though “alone” was not explicitly present in the Greek text. MacCulloch writes that Luther “made no bones about adding ‘only’ to ‘faith.’” MacCulloch, PDF p. 174 (file not included in this release)
Luther’s defense was essentially that:
- “Faith alone” accurately expressed Paul’s intended contrast between faith and works.
- German idiom required something like “alone” to communicate the meaning naturally.
- The larger argument of Romans supported the addition even though that exact word was absent.
So MacCulloch was not saying that Luther simply believed something with no scriptural support. He was showing that sola fide was a theological interpretation of Scripture, not a phrase mechanically copied from it.
Luther allowed the doctrine to judge parts of Scripture
The more provocative part of MacCulloch’s discussion is that Luther’s commitment to justification by faith sometimes governed which biblical books he considered most valuable.
Luther gave priority to:
- John;
- Romans;
- Galatians;
- Ephesians;
- 1 Peter;
- the Psalms.
He disliked or downgraded books that seemed to conflict with his distinction between faith and works. He famously called James—where James says that a person is “justified by works and not by faith alone”—a “strawy epistle.” He also disliked Esther and separated 2 Maccabees and other disputed books into the Apocrypha. MacCulloch, PDF p. 174 (file not included in this release)
MacCulloch therefore makes a striking observation:
Luther was so convinced that the gospel meant justification by faith alone that anything contradicting that message had to be subordinated—even when it appeared within Scripture itself.
That is probably the point you remember as “it could not be proven from Scripture, yet it was accepted through faith alone.” More precisely, MacCulloch’s point is that Luther claimed Scripture as supreme authority while simultaneously interpreting and ranking Scripture according to an Augustinian doctrine he believed represented its central message.
Where Augustine enters the argument
Augustine had developed a particularly severe doctrine of salvation during his controversy with Pelagius. Augustine read Paul as teaching that humanity inherited Adam’s corruption and was incapable of earning salvation. God therefore had to choose, through unmerited grace, whom to save. MacCulloch, PDF p. 145 (file not included in this release) p. 146 (file not included in this release)
MacCulloch does not say Augustine had no biblical basis. Augustine relied heavily on Romans and also invoked Ephesians 1:4—God choosing people “before the foundation of the world.” But MacCulloch shows that Augustine moved beyond the explicit wording of those texts:
- he treated original sin as a hereditary corruption transmitted through procreation;
- he concluded that fallen humanity was entirely incapable of meriting salvation;
- he developed unconditional predestination;
- his logic implied the predestination of the damned, although MacCulloch notes that Augustine rarely stated that implication explicitly;
- his understanding of an immutable God was influenced by Platonism as well as Scripture. MacCulloch, PDF p. 147 (file not included in this release)
Thus the full Augustinian system was scripturally argued, but it was not merely a quotation of Scripture. It was an interpretive theological construction shaped by Paul, Augustine’s dispute with Pelagius, and Greek philosophy.
The historian’s quotation you may remember
MacCulloch quotes the historian of theology B. B. Warfield:
“The Reformation, inwardly considered, was just the ultimate triumph of Augustine’s doctrine of grace over Augustine’s doctrine of the Church.”
MacCulloch, PDF p. 149 (file not included in this release)
The meaning is that Augustine had left Western Christianity two powerful inheritances:
- Augustine on grace: humanity cannot save itself; salvation depends entirely upon God.
- Augustine on the Church: Christians must submit to the Catholic Church, its sacraments, bishops, and institutional authority.
Luther used the first Augustine against the second. He argued that if salvation is God’s free gift received through faith, then the Church cannot control salvation through indulgences, accumulated merits, priestly sacrifices, or compulsory sacramental systems.
Summary
MacCulloch was not claiming that Augustine or Luther simply rejected Scripture and believed blindly. He was explaining that “faith alone” was an Augustinian interpretation of Paul rather than an exact biblical phrase. Luther became so convinced that this interpretation was the Bible’s central gospel that he added “alone” to Romans 3:28 and downgraded biblical books such as James that appeared to contradict it. The controversy was therefore not simply “Scripture versus tradition,” but a dispute over which interpretation and which parts of Scripture should control the rest.