C.S. Lewis's Warning to Christians Who See Sexual Sin as 'the Supreme Vice'

In 'Mere Christianity,' C.S. Lewis explained that 'sins of the spirit' are more destructive than sins of the flesh.

The idea of sexual sin is deeply rooted in the Bible and Christian theology. I think few argue that adultery and fornication are, shall we say, strongly frowned upon in Scripture. We hear about it a lot, in churches, media, and daily conversations.  

One could argue that a casual non-Christian observer could even be partly excused for (falsely) believing that the Christian doctrine can primarily be summed up as, “Thou shall not put that there.”

This is of course not true. So it bears asking, is there too much focus among Christians on “sins of the flesh”?   

In the four Christian Gospels, after all, Jesus of Nazareth spends very few of his words on sexual sin and none of his powerful parables. On the other hand, he spends a great many words and parables teaching love, forgiveness, and grace. Many more are spent chastising the men he viewed as legalistic hypocrites; those who in Christ’s opinion falsely believed themselves to be holy, good, and pure.  

The Christian theologian C.S. Lewis, writing in Mere Christianity, also seemed to suggest that “trespasses of the flesh” are often overemphasized in the Christian hierarchy of sin.

This is what he had to say:

…[T]hough I have had to speak at some length about sex, I want to make it as clear as I possibly can that the center of Christian morality is not here. If anyone thinks that Christians regard unchastity as the supreme vice, he is quite wrong. The sins of the flesh are bad, but they are the least bad of all sins.

Greater sins, in the opinion of Lewis, are sins of the spirit. What are those? He offers us an answer:

[T]he pleasure of putting other people in the wrong, of bossing and patronizing and spoiling sport, and back-biting, the pleasures of power, of hatred. For there are two things inside me, competing with the human self which I must try to become. They are the Animal self and the Diabolical self. The Diabolical self is the worse of the two. This is why a cold, self-righteous prig who goes regularly to church may be far nearer to hell than a prostitute. But of course, it is better to be neither.

I wonder if a careful look at these messages would not give some Christians pause. Humans in general tend to view themselves as basically good. We tend to feel this way even if we are able to recognize our own failings, which often include (if we are truly honest) back-biting, power hunger, and selfish hearts that can cause spasms of hatred. These failings, even if they are only occasional, are of course the very sins that Lewis says are worse than sins of the flesh.

All that said, it should be stated that “sins of the flesh” have the potential to cause great harm. The Bible makes it clear that sin is not just an affront to God; it is also an agent that enslaves and destroys. Even non-Christians, I think, would concede that there is a highly destructive component to lust and adultery.

So what’s the answer? Is a hyper-focus on sexual sin evidence of spiritual pride? Does it obfuscate the greater Christian goal of becoming “conformed to the likeness of the Son”?

Or, considering the destructive nature of sexual sin, is such an emphasis actually prudent?