In A Preface to Paradise Lost (1942), C.S. Lewis notes that the divine laughter directed at Satan in John Milton's epic poem has offended some readers. Lewis defends the laughter, however, and judges it a mistake to think that Satan should have licence to rant and posture on a cosmic scale without arousing the comic spirit: 'The whole nature of reality would have to be altered in order to give such immunity, and it is not alterable. At that precise point where Satan . . . meets something real, laughter must arise, just as steam must when water meets fire.' This comment portends the central themes in a more popular and widely read book Lewis published four years later, namely, The Great Divorce. Written as a reply to The Marriage of Heaven and Hell by William Blake, Lewis's title encapsulates his essential message that Blake's imagined marriage is doomed from the start by the nature of unalterable reality. The divorce Lewis reckons 'great' is not the tragedy of putting asunder what God has joined together, but rather the futile, and in some ways comic, attempt to marry what cannot possibly be united. He terms it a 'disastrous error' to believe that 'reality never presents us with an absolutely unavoidable “either - or”', or to imagine 'that mere development or adjustment or refinement will somehow turn evil into good without our being called on for a final and total rejection of anything we should like to retain'.