[papertyger]

There are many doctrines accepted by Catholics and Protestants alike that do not appear in a spelled-out form. The holy Trinity comes to mind.

The doctrine of the Trinity never rested on Scripture for the Catholic Church. Even so, the observation is irrelevant to supporting your original contention.

Do you concede?

Incidently, I am curious: would you argue against the sufficiency of Scripture?

Absolutely. I should think that would be obvious.

[Lexinom]

Concede what, exactly?

What besides Scripture and what is contained therein would you seek? What would you as a man add to God's written Word?