...and how exactly do you authoritatively know which particular ones those are?
The question of the Romanist presupposes God’s need for a human agency to declare infallibly a list of canonical books. Rome creates this for very overt purposes, to insist that only an “infallible” church can infallibly pronounce such a canonical list. It is a made up and self-serving apologetic that hopes their assertion that Protestants have no answer for this "dilemma". Don't take the Romanist's bait playing this shell game. Rome would have us believe God is not able to make Himself known sufficiently.
The objective authority inherent of Scripture itself, grounded in the reality of Divine authorship, coupled with the internal testimony of the Holy Spirit ratifying the truth of the text, implies believers themselves recognize the divine authority of Scripture.
God alone is a fit witness of Himself in His Word, so also the Word will not find acceptance in men’s hearts before it is sealed by the inward testimony of God the Holy Spirit.
God needs no dependency on His creatures to identify infallibly His own authoritative word (1 John 5:9). The God-breathed word of God is therefore self-authenticating, needing no human sanction. In direct opposition to 1 John 5:9, Rome would presume its witness is greater than God's.
The Romanist "apologist" asks for us to show him the table of contents of the Bible, ready and waiting to strike with some nonsense that Rome declared the canon and without her we would all be bereft. I am reminded of Genesis 3:1 when Romanists attempt this ploy, for theirs is but a variation of the devil's own method to subvert what God has said.
Rather, to Rome's self-serving tactic, we respond that the authority of Scripture, for which it ought to be believed, and obeyed, does not depend upon the testimony of any man, or church, but entirely upon God (Who is truth itself) the Author of Scripture. Therefore Scripture is to be
received, because it is the Word of God (2 Pet. 1:19, 21, 2 Tim. 3:16, 1 John 5:9, 1 Thess. 2:13).
AMR