I am here to debate the scriptural validity of doctrine, not people. This is very hard to do if you don't know upon what your opponent's doctrine is based. If someone wants to defend the Trinity from scripture, but they don't hold scripture to be the final arbiter of doctrine, then what's the point?
Where in Scripture is 'sola scriptura' taught?
-A8
Well, enjoy yourself. But do please understand that there might be folks here for some other reason or reasons. And it may help you to know that it SEEMS that you are here to triumph in a debate, and that the desire for triumph and the frustration that some interlocutors might not want to play your game exactly your way tempts you to provocative misconstructions of what those who disagree with you are saying.
If someone wants to defend the Trinity from scripture, but they don't hold scripture to be the final arbiter of doctrine, then what's the point?
I'm assuming that by "The Trinity" you mean "the doctrine of the Trinity". The Trinity itself needs no defense.
The purpose of that smart-alecky comment is to convey that in discussions of this kind, precision of language, an avoidance of extravagant claims, and a willingness to seek for nuance and the occasional tertium quid will cover a multitude of sins.
For example, the phrase "final arbiter of doctrine" may be about as applicable to the Catholic understanding of role of Scripture as "love" may be to the way I related to my teenager, when I had one -- that is, it's not as simple as it may first appear or as you might like it to be or wish it were.