Sheldon Vanauken chronicled his journey from agnosticism to faith in a personal diary. In his book, A Severe Mercy, describing the struggle to come to faith and dealing with the tragedy of his wife of 17 years, he shared some of the entries of his diary. It was while studying at Oxford that he and his wife became friends with several young students who were believers. It was here that his heart began to be opened. Most influential to his conversion was his friendship with C. S. Lewis.
One of the most astute entries into his diary, while he was still yet an agnostic, was his poignant and cogent observation about what he determined to be the best and the worst argument for Christianity. I have cited it on numerous occasions over the last 30 years - it is one of my favorite quotes. He wrote:
"The best argument for Christianity is Christians: their joy, their certainty, their completeness. But the strongest argument against Christianity is also Christians--when they are sombre and joyless, when they are self-righteous and smug in complacent consecration, when they are narrow and repressive, then Christianity dies a thousand deaths. But, though it is just to condemn some Christians for these things, perhaps, after all, it is not just, though very easy, to condemn Christianity itself for them. Indeed, there are impressive indications that the positive quality of joy is in Christianity--and possibly nowhere else. If that were certain, it would be proof of a very high order."
We must learn this lesson! We are made for a better world as a new creation in Christ. Thus, our journey through this world takes on, in a sense that joy we experience, as we look forward to a vacation where we can, as we sometimes say "can get away from it all" (meaning the stress, frustration and vexation of this world). Faithful Christians, like those going on a vacation, are filled with the prospects of eternity and want to share the excitement of their journey with all who will listen. It is precisely because our citizenship IS in heaven that we are filled with joy, as we journey through this world of darkness and tragedy.
If the Christian's citizenship in heaven means anything, it means that Christians are a colony of heaven on earth. They do not take their cue from the vexation of this world's ungodliness. To the contrary, in every way, as a member of Heaven's colony on earth, they take their cue from that higher and better ground of their hope in the Lord, rejoicing always letting their sweet reasonableness be known in every word and action (Philippians 2:14ff; 3:20-21; 4:4-5; John 13:34ff).