I agree that either something is or is not, no 3rd option there. Still, every kind of argument, positive and/or negative can`t exist solely on words, there needs to be something to back up each argument. Therefore the burden of proof relies on each side of the argument. So, it isn`t that simple. In the end, how does one reach a conclusion?
The basis of any given ethical system is to see men as an end per se and not a means. That`s how reach a universal stand point, as humans are equal. If you take that out then there can`t be universality (spealling?). Any ethical system must see one man and all man alike; consider one and speak about all.
I don`t know a lot of ethical systems but the ones that i know and that rightfully call themselves universal don`t necessarily differ much from one another. The biggest issue here that people seem to forget is, first, the source of that ethical system and second, it`s understanding (moral rules ans moral principles).
In the Christian ethical systems, the core of that system is the result of an act of revelation by God and Jesus. And what we were shown is that God spoke to all humanity - are basis for it being universal. But there`s more than just that. We believe that we were made in God`s image, so we get Love, Unity (in us all as equals, as sons of God), Respect, Dignity, etc. as core values. What then changes is how we understand, and as a result, express that understanding - through one simple commandment that Jesus left us with: love one another like I loved thee.
God and Jesus' actions upon our lives is the basis of our ethical system.
So, in essence, our ethical system is not a construction but a revelation - something a priori.
It`s also not a question of choosing the best but feeling it is the best for you.
There are more proofs of God than just the Bible. There are miracles, Apparitions well documented (with many not considered true by the Church) that make God present to this day and not all are just visions of a single person.
Actually this part is pretty much set aside by most arguments about religions and it`s need to prove itself, that and that the concept of faith is never truly explored.