People sometimes think of Christian morality as a straitjacket—as if God has given us arbitrary commands that we must keep in order to prove our devotion to him. Following God’s instructions (especially in matters related to sexuality) requires us to sacrifice what we truly want, or to squelch our desires, in order to show God how much we love him. We are to give up what we want and obey him instead.

Reading through the collected letters of C. S. Lewis this year, I came across this gem in a letter from Lewis to his lifelong friend, Arthur Greeves, on September 12, 1933. Lewis was no stranger to lust and sexual temptation, and neither was Greeves, who experienced same-sex attraction.

But Lewis believed that the “Christian morality is arbitrary” perspective doesn’t go deep enough. It doesn’t consider what we really want. Neither does it deal with what God really wants. He uses his dog as an example:

“Supposing you are taking a dog on a lead through a turnstile or past a post. You know what happens (apart from his usual ceremonies in passing a post!). He tries to go to the wrong side and gets his head looped round the post. You see that he can’t do it, and therefore pull him back. You pull him back because you want to enable him to go forward. He wants exactly the same thing—namely to go forward: for that very reason he resists your pull back, or, if he is an obedient dog, yields to it reluctantly as a matter of duty which seems to him to be quite in opposition to his own will: though in fact it is only by yielding to you that he will ever succeed in getting where he wants.”

I wish I’d come across this illustration sooner, because I would have included it in This Is Our Time as an example of one of my book’s main pointsthat underneath the myths we believe and the actions we perform are both longings and lies.

The dog believes the lie that the only way forward, the only way to get what it wants, is to push ahead. Lewis, the dog-owner, affirms the longing of the dog to go forward, but he must pull the dog back in order for it to actually make any progress.

Lewis Talks to His Dog

Next, Lewis explains what he would say to his dog, if suddenly it became a theologian and was frustrated by the owner’s thwarting of its will:

“‘My dear dog, if by your will you mean what you really want to do, viz. to get forward along the road, I not only understand this desire but share it. Forward is exactly where I want you to go.

“‘If by your will, on the other hand, you mean your will to pull against the collar and try to force yourself forward in a direction which is no use—why I understand it of course: but just because I understand it (and the whole situation, which you don’t understand) I cannot possibly share it. In fact the more I sympathize with your real wish—that is, the wish to get on—the less can I sympathize (in the sense of ‘share’ or ‘agree with’) your resistance to the collar: for I see that this is actually rendering the attainment of your real wish impossible.’

God Shares Our Ultimate Desire

Lewis applies this parable to our own situation. As human beings, we long for happiness, yet believe the lies that lead to evil actions:

“God not only understands but shares the desire which is at the root of all my evil—the desire for complete and ecstatic happiness. He made me for no other purpose than to enjoy it. But He knows, and I do not, how it can be really and permanently attained. He knows that most of my personal attempts to reach it are actually putting it further and further out of my reach. With these therefore He cannot sympathize or ‘agree’: His sympathy with my real will makes that impossible. (He may pity my misdirected struggles, but that is another matter.)

So, over against the person who says, “I must squelch my desires, out of duty to God” Lewis says, No, God actually shares your ultimate desire. He is redirecting your path so you can actually find that joy you long for.

And over against the person who says, “God affirms me as I am and sympathizes with all my desires,” Lewis would say, No. Because God affirms your ultimate desire, he must categorically reject your sinful actions and desires, for they will forever keep you from what you really want.

The Longing for Joy and the Lie of Sin

What’s the takeaway? First, Lewis says we can look back at our history and see there is a God-given longing behind many of our sinful actions.

“I may always feel looking back on any past sin that in the very heart of my evil passion there was something that God approves and wants me to feel not less but more. Take a sin of Lust. The overwhelming thirst for rapture was good and even divine: it has not got to be unsaid (so to speak) and recanted.”

But now Lewis exposes the lie: the idea that giving into your sinful, illicit lust will fulfill that longing:

“But [the thirst] will never be quenched as I tried to quench it. If I refrain—if I submit to the collar and come round the right side of the lamp-post—God will be guiding me quickly as He can to where I shall get what I really wanted all the time.”

The Gracious, Ruthless God

Second, Lewis says this parable applies to future temptation, and helps us understand why we should expect God to be ruthless in condemning our sin:

“When we are thinking of a sin in the future, i.e. when we are tempted, we must remember that just because God wants for us what we really want and knows the only way to get it, therefore He must, in a sense, be quite ruthless towards sin.

“He is not like a human authority who can be begged off or caught in an indulgent mood. The more He loves you the more determined He must be to pull you back from your way which leads nowhere into His way which leads you where you want to God. Hence MacDonald’s words ‘The all-punishing, all-pardoning Father’.”

It is impossible to appeal to God’s “love” in order to affirm you in your lusts. God cannot and will not affirm your sinful desires and actions because to do so would make it impossible for you to know true joy.

So what should you do when you fall into sin? Ask for forgiveness and redirection.

“You may go the wrong way again, and again He may forgive you: as the dog’s master may extricate the dog after he has tied the whole lead round the lamp-post. But there is no hope in the end of getting where you want to go except by going God’s way.”

Longings and Lies in Our Lust

This parable about the dog helps us see both the longings and the lies in the world’s understanding of sexuality, and it smashes the idea that God wants to kill our joy or obliterate all our desires. Far from it! Instead, Lewis believes that God pulls back the collar precisely because He wants us to find the delight we crave, in Him:

“I think one may be quite rid of the old haunting suspicion—which raises its head in every temptation—that there is something else than God, some other country into which He forbids us to trespass—some kind of delight which He ‘doesn’t appreciate’ or just chooses to forbid, but which would be real delight if only we were allowed to get it. The thing just isn’t there. Whatever we desire is either what God is trying to give us as quickly as He can, or else a false picture of what He is trying to give us—a false picture which would not attract us for a moment if we saw the real thing.

“God knows what we want, even in our vilest acts. He is longing to give it to us. He is not looking on from the outside at some new ‘taste’ or ‘separate desire of our own.’ Only because he has laid up real goods for us to desire are we able to go wrong by snatching at them in greedy, misdirected ways. . . .

“Thus you may well feel that God understands our temptations—understands them a great deal more than we do. But don’t forget MacDonald again—’Only God understands evil and hates it.’ Only the dog’s master knows how useless it is to try to get on with the lead knotted around the lamppost. This is why we must be prepared to find God implacably and immovably forbidding what may seem to us very small and trivial things.”

God understands our temptations. He knows our hearts better than we do. He sympathizes with our ignorant attempts to find joy apart from him. But in his great love, he refuses to affirm us in our misdirected ways. To do so would be to abandon us to the leash and lamppost, where we would strangle ourselves.