Excerpt from Mere Christianity by C.S. Lewis
“The sins of the flesh are bad, but they are the least bad of all sins. All the worst pleasures are purely spiritual: the pleasure of putting other people in the wrong, of bossing and patronising 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. That 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. “
Me Thinking Out loud:
C.S. Lewis makes the comment that there are two forces with in us trying to make their dominance known. They are the Animal Self and the Diabolical Self. He doesn’t really define these ‘self’s’ but I would assume that the animal self is more about instinctive sin nature and the diabolical self is the deliberate sin nature of the spirit. He says both are bad but that the Diabolical Self is much worse. He prefaces all this by saying that sins of the spirit are much worse than sins of the flesh and again I am assuming that he means the Animal Self refers to the flesh and the Diabolical Self refers to the spirit. My quandary is now one of a sin measurement system that he seems to be introducing. Is it possible that he is really saying that there are worse sins than others? Maybe in human eyes that is very possible. In God’s eyes, I’m going to have to say “sin is sin” and it all leads to a spiritual death. So, why bring this up in the book? C.S. Lewis was a very learned man and likewise highly respected; I can’t imagine him actually endorsing a measuring system for sin. The only thing I have been able to come up with so far is that once you’ve allowed your Diabolical Self to have control, it is a gateway to all other sins and thus encompasses even the Animal Self.
Living Out Loud 
I believe the reason why C.S. Lewis is calling the sins in spirit worse than the sins of flesh is because the sins in spirit are hidden and therefore have a much greater power to control you. When you sin by flesh, you know that you are doing wrong, but by spirit you don’t always know that – and that gives the devil a much bigger platform to control you.
Reblogged this on Blue-Brown Books and commented:
I ran across this post the other day, and it struck me that this girl doesn’t really have a very clear understanding of what C.S. Lewis was trying to say.
Yes, sin is sin, but he’s not trying to say it’s not. He’s making the distinction between two parts of every human being…the “Animal Self’ – that is, the part of us that acts on instinct (going in search of food and drink, sex/intimacy, companionship, shelter, etc.). This part (to my way of thinking) is not INHERENTLY sinful, but it can BECOME sinful if we do not put these instinctual wants and desires under the control of the Holy Spirit.
And then there’s the “Diabolical Self,” which (again, as I understand it) is our SIN NATURE. It is INHERENTLY evil. It is the part of us that (thanks to Adam) has gone against God from the beginning. But (thanks to God and His free gift of grace through His Son, Yeshua) even though Adam ruined it for us all, Yeshua’s perfect obedience and perfect sacrifice made it possible for us all to be righteous in God’s sight (Romans 5:12-21).
Our instincts don’t blind us to the truth of who we are and what we need, but our own prideful, spiritual self-righteousness can. I think that’s Lewis’s point (and, indeed, Yeshua made a similar point in Luke 18:9-14). But, thank God, we can put to death both the Animal and the Diabolical Selves by the power of the Holy Spirit.
When I read scripture it seems like Christ speaks of sin that can be deadly (separating us from God) and sin (breaking the least of commandments) that is not deserving of hell (separation from God).
Paul also seems to think that some sin is deadly and we would need to pray for those committing deadly sins for the grace of repentance… So they can come back into the body of Christ and be in union with God and fellow Christians again. If it is not deadly
sin, Paul says we can pray in a different way for our brother or sister.
I John 5:16-18:
If anyone sees his brother committing a sin that is not a deadly sin, he will ask, and God will give him life for those whose sin is not deadly. There is sin which is deadly; I do not say one is to pray for that. All wrongdoing is sin, but there is sin which is not deadly. We know that anyone born of God does not sin, but He who is born of God keeps him, and the evil one does not touch him.”
By saying Diabolical Self sins are worse, I think he means that they are harder to recognize than the obvious “animal sins” because of their insidious and abstract nature… we can actually commit diabolical sins and think we are “right”..