How do those who cite 2 Tim 3:16 to prove the inspiration of Scripture know that 2 Tim 3:16 is itself inspired and what is meant by "All Scripture"?

I really like the approach of asking people Socratic questions as a means of gaining deeper insight into why they believe what they believe. For example, when I've asked people to explain to me how they know that the Bible is divinely inspired, many times I've had 2 Timothy 3:16 cited to me as an answer: > 16 **All Scripture is breathed out by God** and profitable for teaching, for reproof, for correction, and for training in righteousness, 17 that the man of God may be complete, equipped for every good work. [2 Timothy 3:16-17, ESV] To those who consider that citing 2 Timothy 3:16 is a valid response, I would like to ask them two follow-up questions: - How can we know for sure that 2 Timothy 3:16 is itself divinely inspired? - How can we know for sure what is meant by "All Scripture"? What writings are included in that statement and why? ___ Related: https://christianity.stackexchange.com/q/83868/50422