“First of all, you don’t know what the thief on the cross knew or did not know. So out goes that argument.”
That you cannot answer it in the affirmative doesn’t invalidate the question - or its OBVIOUS answer.
“However, is the Triune God revealed in the Old Testament?”
Most Jews would say no. They would tell you the plurality is used to show greatness. And the details as found in the Athanasian Creed were developed by philosophers discussing God. The details are certainly not explicitly taught in scripture.
Before you or anyone else hyperventilates, I’m not denying the doctrine of the Trinity. But that doctrine, as discussed in the Athanasian Creed, is one a lot of believers could not pull out of scripture even with years of reading and thinking.
Why?
Because God is not a fit subject for human dissection. God does not reveal systematic theology because God knows theology doesn’t change lives. We are explicitly taught we are sinners, we need to repent, we need to be forgiven and need to let God change us from within. We need faith, not in creeds, but in GOD.
Believer’s baptism is clearly taught in scripture. Yet many deny it, including the Catholic Church. The need for the baptism of the Holy Spirit is clearly taught, and indeed, no one can be a Christian without it, yet theologians largely ignore it.
15 The Holy Spirit also testifies to us about this. For after He says:
16
This is the covenant I will make with them
after those days, says the Lord:
I will put My laws on their hearts
and write them on their minds,
17 He adds:
I will never again remember
their sins and their lawless acts.
18 Now where there is forgiveness of these, there is no longer an offering for sin. - Hebrews 10
God is interested in our changed lives. He is not interested in our ability to dissect Him.
I’ve never heard or read a sermon by Andy Stanley. Don’t know if he is a heretic or believer. But saying a person can be saved without knowing about the Virgin Birth is hardly radical. It ought to be obvious. It also should be obvious that the important point about Christmas isn’t the Virgin Birth, but that God came to earth to save us from sin.
God saves us. Theology does not. If you doubt me, look to the seminaries filled with unbelievers. Look at the church doctrines that accept sprinkling babies as a true baptism and get back with me about how theological discussions save souls.
“Before you or anyone else hyperventilates ...”
It seems to me that you are the one doing the hyperventilating. Why did you drag “believer’s baptism” into this?
If you can’t stick to the point at issue, there is no discussion. The exercise simply turns into something akin to a cable “news” program of two talking heads exchanging ranting monologues.