I love this story about how C.S. Lewis’s desire to be a good teacher prevented him from resting in a generic theism. It helped to “force” him rationally into something, which was eventually Christianity.
As long ago as 1920, his study of philosphy had led him ‘to postulate some sort of God as the least objectionable theory’, though he added, ‘of course we KNOW nothing’. The notion of an ultimate truth made sense to him because, as he remarked in 1924 when commenting on Bertrand Russell’s free-thinking idealism, ‘our ideas are after all a natural product’, and there must be some objective standard, some ultimate fact to explain them.
On the other hand, ‘God’ still seemed a crude and nursery-like word, and for several years Lewis used other terms to describe his notion of fundamental truth. During this time he was, like most othose who studied philosophy at Oxford in the early nineteen-twenties, still accepting the work of Hegel and his disciples, and as a result he chose Hegelian expressions such as ‘the Absolute Mind’ or just ‘the Absolute’.
But when he spent the year 1924-5 teaching Philosphy at University College he discovered that this “watered Hegelianism’ was inadequate for tutorial purposes. The notion of an unspecified Abolute simply could not be made clear to his pupils. So he resorted to referring to fundamental truth as ‘the Spirit’, distinguishing this (though not really explaining how) from ‘the God of popular religion’, and emphasising that there was no possibility of being in a personal relationship with this Spirit…
It was finally in 1929 that he first knelt and prayed to this God.
-Humphrey Carpenter, The Inklings, p.41