In a 1990s movie, “City Slickers,” there’s a scene that sheds light on the importance of private integrity. Three men, New Yorkers, close friends, have gone off together for a summer to ride on a cattle drive in the hope that this experience will help them sort through their respective midlife issues.

At one point, riding along on the trail, they are discussing the morality of having a sexual affair. Initially their conversation focuses mostly on the fear of getting caught, and two of them agree that an affair isn’t worth the risk. You’re too likely to get caught. But their friend poses the question again, this time asking them if they would have an affair if there was the absolute assurance that they wouldn’t be caught:

“Imagine,” he says, “that a spaceship touches down. A beautiful woman emerges from the spaceship. You make love and she returns to Mars. There are no consequences. Nobody can possibly know. Would you do it?”

Billy Crystal, who plays the lead role, answers that he doubts that this is ever possible. “You always get caught,” he submits, “people smell dishonesty on you.” “But,” his friend protests, “what if it was really possible to have an affair and not get caught. What if nobody would know? Would you do it?” Billy Crystal’s answer: “But I’d know, and I’d hate myself for it!”

His answer highlights an important truth. What we do in private, in secret, has consequences that are not dependent upon whether or not our secret leaks out. The damage is the same. What we do in secret molds our character and influences how we relate to others in more ways than we suspect. There is no such a thing as a secret act. One person always knows. We know. And we hate ourselves for it, hate ourselves for having to lie. And this gives off its own scent.

What we do in secret ultimately shapes what we look like in public. Dishonesty changes the way we look because it changes who we are. That’s the reason why so often those around us will intuit the truth about us, smell the lie, even when they don’t have any hard evidence on which to suspect us.

Doing something in secret that we can’t admit in public is the very definition of hypocrisy, and that forces us to lie. And, among all sins, lying is the most dangerous. Why? Because we hate ourselves for it, stop respecting ourselves, and when we stop respecting ourselves we will, all too soon, notice that other people stop respecting us too. That’s the intuitive place where we “smell” one another’s lies.

Worse still, lying forces us to harden ourselves so that we can live with our lie. Sin doesn’t always make us humble and repentant. We have the all-too-easy, popular image of the honest sinner, like the sinners in the Gospels who more easily accepted Jesus than did the religiously upright. That’s sometimes the case, but not always.

The biblical image of the honest sinner humbly turning toward God is predicated on honesty, on a sinner not hiding or lying about his or her sin. But sin can have a very different effect on us.

When we don’t honestly admit our sin, we move in the opposite direction, namely, toward rationalization, hardness of attitude, and cynicism. Moreover, it’s the lying, not the original weakness, that then becomes the real canker and constitutes the real danger. When we hide a sin, we are forced to lie, and with that lie we immediately begin to harden and reshape our souls.

There’s a moral axiom that says: You can do anything as long as you don’t have to lie about it. That’s quite different from saying that you can do anything as long as nobody finds out about it.

The quality of our person depends upon the degree of our private integrity. We are as sick as our sickest secret, and we are as healthy as our most hidden virtue. We cannot be doing one thing in private and radiate something else in public. It doesn’t matter whether others know our secrets or not. We know and, when those secrets are unhealthy, we hate ourselves for them and our hearts harden so as to live with our lies.

We should never delude ourselves into thinking that the things we do in private, including very small actions of infidelity, self-indulgence, bigotry, jealousy, or slander, are of no consequence since no one knows about them. Inside the mystery of our interconnectedness as a human family and as a family of faith predicated on trust, even our most private actions, good or bad, like invisible enzymes inside the bloodstream, affect the whole. Everything is known, felt, in one way or another. There is no such thing as a private act, inside the family of humanity or inside the body of Christ.

Others know us, even when they don’t exactly know everything about us. They smell our vices, just as they smell our virtues.