Lewis was a convert to Christianity. The usual self-analytical deficiencies of religious believers are often gigantified in converts, possibly because they adopted their beliefs out of need rather than simple habit and thus will hug them much tighter.
This is our monthly thread for collecting these little gems and pearls of wisdom, rationality-related quotes you've seen recently, or had stored in your quotesfile for ages, and which might be handy to link to in one of our discussions.