Lewis in The Lion and the Fox (1927):

tragedy is not the purest art. The contests of pure art would be like the battles of the norse heroes in heaven. They would ride back after the battle to Valhalla or some more congenial Elysium, the wounds and deaths abolished by magic at the termination of each day. Only heroes would participate; and no reality would mar their vigorous joys.¹

Lewis was favorably disposed to Catholicism, but never converted. The reason may have been given in this passage with “no reality would mar their vigorous joys”.

Lewis’ “battles (…) in heaven”, like McLuhan’s “ancient quarrel”, was a reflex of Plato’s gigantomachia in the Sophist. There, too, an unending battle of superhuman forces is always taking place.  But the third ancient power in Plato’s telling is the philosophical child “begging for both” who would join the other two endlessly warring parties in a basic harmony.  Similarly with McLuhan:

Paul Claudel, of course, is not bound by these dichotomies of space and time, the vertical and horizontal. (…) Claudel’s thought and poetry obviously move freely in both (…) He values equally [ie, grammatically] the resources of dialectic and continuous discourse [ie, rhetoric]. He can therefore be both (…) for [him] Time and Space are not sectarian problems.²

Lewis apparently thought that the unending force and beauty of the fundamental powers could be preserved only through their isolation and complete separation from “reality”. In fundamental contrast, the “both” of Plato, and of Claudel in McLuhan’s telling, was not restricted to one power of the three in the “ancient quarrel”, but instead also characterized the essential outpouring of that quarrel and of all its protagonists into crass “reality”. It was exactly this fundamental urge to manifestation linking possibility with actuality that Aristotle expressed in his dynamics and that was carried over into Christianity as “incarnation”.