I cannot think of a more challenging question for a Christian. It makes us wonder if we have anything to say to a person who is not a Christian that would at least encourage him or her to consider becoming one. It also makes us think about why we ourselves are Christians.
Whenever we talk with a non-Christian, it is more important to witness than to convince. We should listen to his or her story and, when we hear some question that comes from that person's experience, then we may share how the Gospel of Jesus Christ has enabled us to respond to that question in our own lives.
In the end, ultimately everything is a mystery. Religions always will exist because their response to the mystery of being is to offer another mystery to explain it. There is no escape from being enveloped in mystery, and we who are Christians have discovered that the mystery that makes the most "sense" out of the mystery of being is the mystery of God who is revealed in Jesus Christ.
I invite you to read the whole thing. Consider this as you do. Bishop Whittaker is using what I would consider wonderfully pragmatic ways of understanding Christianity as a way of being human, rather than arguing a position from some set of principles. In acknowledging that the question should force us to examine our own faith life, he surrenders any recourse to doctrine, or the circular "because the Bible says so" apologetics we find too often. We are to look first to the Jesus we encounter in the Gospels, always keeping the discrepancies and differences among them clearly in mind. We are to look at the question, the call, inherent in this encounter not as some bit of intellectual content to which we give assent, but a pragmatic question of whether or not to allow this encounter to change our lives.
I commend Bishop Whittaker as a wonderful example of liberal, pragmatist Christian faith.
Even if he doesn't know it.