Now that the Centenary Forum has concluded and everyone has had a chance to respond to the lecture by Erik Wielenberg, a philosophy professor from DePauw University, I'll take the opportunity to give my two cents.
Wielenberg argued that God is not necessary to have a sense of objective morality. I have had a hard time constructing a response because I've never taken any philosophy and I don't speak that language. I can come at it from a theological perspective, so that's what I'll try here.
In a way, I think Wielenberg is correct. You don't have to believe in God to live by a specific moral code. I have known plenty of non-believers, who still have a highly developed sense of right and wrong and who would normally be considered "good people."
However, God's existence doesn't depend on our belief. In the prologue to the Gospel of John, the writer says "He was in the world, and though the world was made through him, the world did not recognize him." God is there in our lives and our decisions and the world around us whether or not we believe.
Wielenberg is operating under a faulty assumption of who or what God is. He said in his lecture that if there is a God, it is an external force who guides creation. He tends to impose human characteristics on God, who is clearly operates in ways unknown to people. I believe God is much more infused in his own creation.
God did not just create morality and truth -- God IS morality and truth. In the book of John, Jesus says "I am the way and the truth and the life." And, by definition, objective morality or objective truth assumes that there is only one truth. Therefore, whenever we seek truth whether in Christianity, Islam or atheism, we will find God.