What is Truth?

Well, the obvious answer is "Jesus." He is the Truth. So I guess a better question is, "What are the foundational truths that make us Christian that we cannot question without straying from the Christian faith?" The problem is that no one agrees on what the foundational truths are. Must you believe that Jesus is 100% man and 100% God? According to the Council of Nicea, yes. So are all the Copts not Christians? Even at Nicea, they argued and voted and the winners decided what was orthodoxy and what was heresy. Must you believe that the Holy Spirit only proceeds from the Father? According to the Orthodox Church, yes. That leaves the entire western church in heresy. I could go on. We must establish a common basis for deciding the foundational truths before we can ever agree on what they are.