"I do not look at myself."
This statement is made by Len, spoken to his earthly friend 'the Big Ghost' in Chapter Four. It should be read as an echo of 1 Corinthians 4:3, for it speaks to embracing grace and laying down pride. By all human standards of right and wrong - virtue and vice - we are incapable of goodness and must therefore discover another standard.
This is what the Big Ghost finds quite difficult, of course, in that he continues to push on for his own so-called rights (based upon his own self-righteous views of morality). He is implored by Len to "stop thinking about it" and embrace this new reality. What is the stumbling block? Len is a murderer, and the Big Ghost knows that he has taken Jack's life. What the Big Ghost is unwilling to accept is that both Len and Jack are waiting for him to join them in the new real world.
Truth and morality come under fire here, for when the context is explained to the Big Ghost - in that he was not in fact a decent man, along with the failed morality of all humanity - the Big Ghost refuses to let go of pride and instead fights for his own sense of ethic. Interestingly, Len further confesses, "Murdering old Jack wasn't the worst that I did. That was the work of a moment and I was half mad when I did it. But I murdered you in my heart, deliberately, for years. I used to lie awake at nights thinking what I'd do to you if ever I got the chance . . ."
Matthew 5:21-22 should come to our minds here, even though a great number of Christians who have brought no deliberate physical harm on another person are guilty of the same kind of murder that Len refers to in his confession. So often we think that what is physical is real, diminishing the spiritual realities which surround us. Perhaps this is why we overemphasize the physical sufferings of Christ and do not adequately understand why he so desired for this cup to be taken from him. The context of this story is a spiritual existence so real that the fallen physical world cannot intrude on it, until it embraces it.
In the end Len confirms to the Big Ghost, "There are no private affairs." Just like the lamp on a stand (Luke 8:17) judgment comes publicly and swiftly. Further, Lewis builds on the tradition (largely lost in Western Christianity) that the work of the church and kingdom is a community affair, and our faith is worked out together.
Having spoken his piece to the Big Ghost, Len joyfully invites him to travel along to the mountains - a happy invite to the world which now awaits. But the Big Ghost still cannot let go of himself and his pride. He is still unable to see the spiritual reality masked behind the fallen physical world in which he lives. And that will be one of the greatest challenges to each character - and to the reader/thinker/theologian - to remove the veil of this reality for the sake of embracing a higher truth.