When I was in seminary, I had many discussions that centered on the question of Pilate: "What is truth?"
There were, and are, many ways to understand that question, and many ways of answering it. Most of those have to do with what we understand the "truth" to be, and how we communicate it to unbelievers such as Pilate was.
These days however I am coming to believe that the key question is not "what is truth?", but "what is man?" That is, the key question is not what truth is as such, as though truth were primarily an existential matter, but what the truth is about us. If we correctly understand what we are we can better understand what the gospel is, and why it is what it is.
I believe that the gospel is what it is because that is the way it has to be in order for us to be saved. Given who and what we are, and Who and What God is, the gospel could only be what is.
So that's what I am thinking. Next time I will go into who and what we are. After that, I'll go into Who and What God is.