Who is George MacDonald from The Great Divorce and what is their importance?

George MacDonald doesn't appear until about halfway through the novel, but next to the narrator, he is the most important character in the book. George MacDonald was a real literary figure, a Christian preacher, poet, and philosopher, whom C.S. Lewis admired and looked up to. The real George MacDonald was Scottish, and C.S. Lewis has preserved that detail, giving the character George MacDonald a Scottish brogue in his conversation.

George MacDonald is jovial and humble. He looks like a shepherd and scholar at the same time, is totally honest and reliable. No matter what atrocity the two encounter, MacDonald is always calm and ready with an explanation when the narrator asks questions. George MacDonald's character can be compared with Dante's Virgil from The Divine Comedy.