A Severe Mercy

Here is a snippet from Sheldon Vanauken's A Severe Mercy, at this point writing as an atheist learning about Christianity:

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 for them.  Indeed, they 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.