CS Lewis: Fictitious Correspondence

Lewis used fictitious correspondence three times:

Ransom writes to Lewis;
Lewis writes to Malcolm;
Screwtape writes to Wormwood.

Of course, in reality, Lewis wrote both Ransom and Screwtape although Screwtape then made a name for himself. Screwtape exists only to write his letters and, later, to propose a toast. Malcolm exists only to receive letters from Lewis. By contrast, Ransom is the central character of a Trilogy and writes to Lewis only at the end of Volume I.

The Screwtape Letters and Letters to Malcolm: Chiefly on Prayer, two entire volumes of fictitious letters, refer to fictitious characters - the man tempted by Wormwood, Malcolm's son who becomes ill - and conventional novels could have been written about these characters. Instead, Lewis used the fictitious correspondence form to address temptation and prayer.

Lewis' fictitious letters indirectly interacted with James Blish's fiction:

(i) In Black Easter, which is in memoriam CS Lewis and includes quotations not only from Lewis but also specifically from Screwtape, a demon announces the death of God. Lewis, of course, could not respond to Black Easter, written after his death, but does tell Malcolm how he would respond to a hypothetical death of God. 

(ii) In The Day After Judgment, the sequel to Black Easter, a magician refers to Screwtape as a real demon communicating with Lewis: an unexpected element of humor in an otherwise horrific scenario.

(iii) Both Lewis' Screwtape and Blish's Goat refer to Satan as "Our Father Below."