"I know it's off the point", Havard interjects, "but I'd like to ask Williams what he would regard as the worst possible sin?"
Williams answers without a moment's hesitation: "The exclusion of love."
From "Thursday evenings" (an imaginative recreation of a meeting, closely based on documentary sources) in The Inklings, by Humphrey Carpenter, 1979.
For many years found Charles Williams's idea of the worst possible sin to be impressive - and yet also puzzling.
(I later came-across the place where Williams gave this judgment, and from-which Carpenter derived the quotation; but unfortunately I have now forgotten where this was published.)
Although for somewhat different reasons than Williams - I also regard "the exclusion of love" as a deep insight into sin, rooted in the ultimate nature of reality.
Therefore, the exclusion of Love is the primary sin; because it rejects and opposes divine creation itself.
This is important, because Men are easily distracted by more 'spectacular' and positive sins; but it is worth remembering that these are (in a sense) just a means to the end of the exclusion of Love.
And also that the exclusion of Love may be at work - as a motivation, in the nature of Men or other Beings - even when spectacular sins are entirely absent.
Many large and powerful aspects of modern life are a material embodiment of the exclusion of Love: such as bureaucracy in general, and social systems such as law, the economy, and mass media...
The modern institution is a domain where procedures dominate. Love is excluded from operations ever-more-completely; and consequently an environment where (Love-less and Love-hating) cold, soulless, psychopathic, manipulative careerists thrive.
And the worst of positive sins is probably spite; and that too can be seen as a consequence of the exclusion of Love.
Where Love is present, spite can never work unopposed; but without Love, spite can become master.