My first assertion, that Sola Scriptura isn't scriptural, he answers thus:
I'm convinced that SS is taught in 2 Timothy 3:12 - 4:5. I commend to you a careful reading of this text. Scripture equips the man of God "for every good work." therefore, no other ultimate source is needed for religious truth. How does Scripture equip you to venerate departed saints?He continues: Still on point 1, you asked: "But on whose authority is that interpretation? It is not scriptural." He answers that thus:
Because Christ is the ultimate authority (thankfully we can agree on that), His Word is the infallible rule for our faith. So where is His Word? It is now written down in the Supreme Apostolic Tradition, Scripture. Can you give me an example of any other God-breathed revelation that's not in Scripture?These all seem fair questions to me, so I shall address them as best I can, with the caveat, as ever, that I am merely a lay person, with no particular theological training, nor the grace of clerical state.
So, here goes...
1: 'I'm convinced that SS is taught in 2 Timothy 3:12 - 4:5. I commend to you a careful reading of this text.'
Scripture equips the man of God "for every good work." therefore, no other ultimate source is needed for religious truth.
The 'therefore' in this sentence actually hides a logical error. For example, a plumber might have a tool box that equipped him for every job he might encounter; but instructions on how to use the tools is also necessary. Scripture is indeed necessary and equips us (no Christian could deny that) but this verse does not teach that it is all that is necessary. If this verse were teaching Sola Scriptura, I would expect to see that Sola represented (Luther had the same problem with Sola Fide: such was his respect for Scripture, of course, that he added in a Sola that he thought the Holy Spirit had somehow overlooked, in his translation...)
3 How does Scripture equip you to venerate departed saints?
There are two parts to this. The first is that I do not concede that Christians are bound by Scripture alone; that is, the Sacred Tradition of the Church, and the formal teaching of the Church, are also authoritative.
However, in this case, we have a clear Scriptural mandate. 'All generations shall call me blessed.' To refuse to venerate the Blessed Virgin Mary is to make a liar of her, in her proclamation that is clearly presented as inspired.
4 So where is His Word? It is now written down in the Supreme Apostolic Tradition, Scripture. Can you give me an example of any other God-breathed revelation that's not in Scripture?
This line of argument risks being slightly circular: I only accept what is in Scripture: can you give me an example of something I accept that is not in Scripture?.... But in practice, of course, we can. Firstly, we need to recognise that all truth is implicit in Scripture, but not all explicit. That is where interpretation is key. And that is why, Catholics believe, the Holy Spirit, as promised by Christ, protects the Church from errors of interpretation.
So, for example, I could cite the doctrine of the Trinity. It is implicit in Scripture, not least in the command to baptise all nations in the name of the Father and of the Son and of the Holy Spirit. But nowhere in Scripture is there explicit teaching that the Father and the Son and the Holy Spirit are three persons in one Godhead. That is an interpretation: guaranteed, I would argue, by the promise of Christ and the working of the Holy Spirit - but an interpretation, nonetheless.
More fundamentally, as I have mentioned before, nowhere in Scripture is a list of the books that make up the Holy Scriptures. Indeed, the list has been subject to dispute. Yet, if we are to take Scripture alone as our infallible authority, surely Scripture needs to define what constitutes Scripture. However, we all accept that the four Gospels (Matthew, Mark, Luke and John) are authoritative, and that the Gospel of Thomas, for example is not. And we do that on the infallible teaching of the Church - which Scripture teaches us is the pillar and foundation of the truth, and which our Lord promised the gates of Hell will never prevail against.
So, to answer the first part of the question, His Word is found both in Sacred Scripture and in the Authentic Apostolic Tradition, and in the formal and magisterial Teaching of the Church. And these three can never be set against each other: they are all consistent and self-consistent, and are all guaranteed by the Holy Spirit, whom Our Lord promised would be with us until the end of all ages.
Finally, I would note, that logic suggests I could be wrong about all of this. However, the fact that I, and millions of others for the past two millenia, could arrive at these beliefs in good faith, through prayerful reading of Scripture, whilst others, also in good faith, through prayerful reading of Scripture, arrive at different conclusions... that fact alone shows that Scripture, without authoritative interpretation, does not, in fact, provide a single rule of faith and belief.