The Trinity is the most fundamental belief of Christian doctrine.

I would like to point out that because the Pro position in this debate is that the doctrine of the Trinity is the most fundamental Christian belief, the Con position in this debate would logically be that the doctrine of the Trinity is NOT the most fundamental Christian belief (and, ideally, would suggest an alternative if that is the case). In other words, the burden of proof lies on me to prove my assertion, while your job is simply to refute my assertion. It appears that you have not even addressed the topic at hand, except to say that my assertion is "Utter nonesense [sic]." This debate is not about anything besides whether the Trinity is the most fundamental doctrine in Christianity. I would greatly appreciate you staying on topic. Perhaps it would also help to define the word fundamental, for the sake of clarity. Fundamental, in this debate, is defined as "forming a necessary base or core; of central importance" (Oxford English Dictionary). I concede that I probably should have defined the term in the first round. Now that I've gotten that bit of housekeeping out of the way, I will continue to argue my case that the Trinity is fundamental, as defined above, to Christian thought. I stated in the first round that without the Trinity, humans would have a miserable, hopeless existence (presupposing that humans were indeed created by God). Allow me to explain. For instance, many people - even some Christians - think of God being a ruler before all else. This view of God implies that humans exist merely to be ruled over, that we were essentially only created to obey the laws that God sets in place. And what would be our motivation to follow these commands, but fear of punishment? We would simply be mindless slaves, obeying to avoid the consequences but never loving God. There would be no hope that we might "have life and have it abundantly," as Jesus puts it (John 10:10, English Standard Version), but only fear that compels us to just keep surviving. So, what does the Bible say about the matter? - "Then God said, 'Let us make man in our image, after our likeness. And let them have dominion over the fish of the sea and over the birds of the heavens and over the livestock and over all the earth and over every creeping thing that creeps on the earth'. So God created man in his own image, in the image of God he created him; male and female he created them" (Genesis 1:26-27). It is clear that we are created to be image-bearers of God, to reflect His character and thus bring Him the glory that He is due. That does include exercising authority over creation - after all, part of God's character is that He is a Ruler - but if we stopped there, we would miss so much more. Note that God says, "AND let them have dominion." Though this dominion is part of our created purpose, it comes because of the overarching purpose of imaging God. If God were fundamentally a Ruler, and if we were still created in His image, then we would be created to rule - contradicting our own identity implied by God's identity. As I discussed in the previous round, God is triune - it is clear once again from this verse: "Let us make man in OUR image. . ." - and is thus loving at His very core. Every other characteristic of God is an extension of this love, including His creativity. Being eternally a Father, God is eternally outgoing and life-giving. It is only natural for God to create as a result, seeking to fill everything in existence with His perfect love. If we are indeed created as image-bearers, then we must be fundamentally created to love and be loved. That is where our flourishing lies: in fulfilling our purpose. There is nothing miserable nor hopeless about it.