Sola Scriptura is self-refuting — walking through the argument

The argument you've outlined touches on a fundamental point of Catholic-Protestant disagreement, and the Church's teaching supports your reasoning.

Scripture itself points beyond itself. St. Paul writes that the Church is "the pillar and foundation of truth" (1 Tim 3:15), not Scripture alone. He also commands the Thessalonians to "hold fast to the traditions you were taught, whether by word of mouth or by letter" (2 Thess 2:15), indicating that oral apostolic teaching carries authority alongside the written word.

The canon question is decisive. The Council of Rome (382), Hippo (393), and Carthage (397, 419) affirmed the 73-book canon, and this was formally defined at the Council of Trent (Session IV, 1546). The Catechism states: "It was by the apostolic Tradition that the Church discerned which writings are to be included in the list of the sacred books" (CCC §120). Without this ecclesial discernment, there is no agreed canon to appeal to.

The Church's position is that Scripture and Tradition form one sacred deposit of the Word of God, entrusted to the Church, with the Magisterium as its authoritative interpreter (CCC §§80–87; Dei Verbum §§9–10). The Second Vatican Council taught that "Sacred Tradition and Sacred Scripture form one sacred deposit of the Word of God, committed to the Church" (Dei Verbum §10).

This does not diminish Scripture's authority — it situates it properly within the apostolic community that received and transmitted it.

The argument presented here is substantially sound and reflects a standard Catholic apologetic critique of sola scriptura.

On the canon: The Church discerned the biblical canon through a process involving apostolic tradition, liturgical use, and episcopal judgment—culminating in councils like Rome (382), Hippo (393), and Carthage (397). The Catechism affirms that "it was by the apostolic Tradition that the Church discerned which writings are to be included in the list of the sacred books" (CCC §120). This means accepting the canon already presupposes ecclesial authority operating outside Scripture alone.

On the self-refutation charge: The Council of Trent taught that divine revelation is transmitted through "written books and unwritten traditions" and that both are to be received "with an equal affection of piety and reverence" (Dei Verbum §9 reaffirms this at Vatican II). The Catholic position is that Scripture is materially sufficient but requires the Church's living Magisterium to interpret it authentically (CCC §85–87). The objection that sola scriptura is not itself taught in Scripture is logically significant—it's a criterion that fails its own test.

A nuance: Some Protestant theologians distinguish between sola scriptura (Scripture as the supreme norm) and solo scriptura (Scripture interpreted apart from any tradition). The stronger versions of sola scriptura are more vulnerable to this critique than weaker ones. But even the weaker forms struggle to account for how the canon was established without binding ecclesial authority.

The post's reasoning aligns with Catholic teaching on Scripture and Tradition.

The strongest Protestant responses typically take one of these forms:

1. The "fallible collection of infallible books" argument — Some Reformed theologians (e.g., R.C. Sproul) concede the canon was recognized through a fallible human process, but argue this doesn't undermine Scripture's intrinsic authority. The Church discovered rather than conferred the canon. This sidesteps the self-refutation charge but raises the question: on what basis can one be certain they possess the right 66 (or 73) books?

2. The self-authenticating Scripture argument — Drawing on Calvin, some argue the Holy Spirit testifies internally to the divine origin of canonical books, making external ecclesial authority unnecessary. The difficulty here is that this criterion is unfalsifiable and was not how the early Church actually proceeded (they appealed to apostolicity, liturgical use, and episcopal consensus).

3. The tu quoque response — "Catholics face the same problem: how do you know the Church is authoritative without an infinite regress?" The Catholic answer is that Christ founded a visible Church with teaching authority (Mt 16:18-19, 1 Tim 3:15), and this is verified historically — not a vicious circle but a coherent web of mutually reinforcing evidence.

The Catechism addresses the underlying issue: "It is not from Sacred Scripture alone that the Church draws her certainty about everything which has been revealed" (CCC §82). Scripture, Tradition, and Magisterium are "so linked and joined together that one cannot stand without the others" (CCC §95, cf. Dei Verbum §10).

Your original argument stands: the canon presupposes the very authority Sola Scriptura denies.