At one point, riding along on the trail, they are discussing the morality of sexual affairs and the dangers inherent in them. 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 are 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 space ship touches down. A beautiful woman emerges from the space ship. 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. Would you do it? What if nobody would ever know?” 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 helps mold our persons and influences how we relate to others in much deeper ways than we suspect. There is no such a thing as a secret act. The most critical person of all always knows. We know. And we hate ourselves for it, hate ourselves for having to lie, and this colors how we relate in general.

What we do in secret ultimately shapes the person whom we present in public. Dishonesty changes the very 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 hypocrisy forces us to lie. And lying, among all sins, is perhaps the most dangerous. Why? Because we hate ourselves for it and we stop respecting ourselves. 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” each others’ lies.

Moreover, 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, someone like the repentant woman who anoints Jesus’ feet. That is sometimes the case and is the case for certain sinners who accept Christ more easily than do many moral, church-goers.

But it doesn’t always work that way. The biblical image of the honest sinner humbly turning towards God is predicated precisely on honesty, on the sinner not hiding or lying about his or her sin. When we don’t honestly admit our sin we move in the opposite direction, namely, towards rationalization, hardness of attitude, and cynicism. Moreover, it’s the lying, not the original weakness, that then becomes the real canker and constitutes the greater danger. When we hide a sin, we are forced to lie, and with that lie we immediately begin to harden and reshape our souls. You can do anything, as long as you don’t have to lie about it. That’s very different than saying that you can do anything as long as nobody finds out about it.

The quality of our persons depends upon the quality of our private integrity. We are as sick as our sickest secret and we are as healthy as our most private virtue. We cannot be doing one thing in private and radiating and professing 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 as we live with our lie.

We should never delude ourselves into thinking that the things we do in private, including very small actions of infidelity, of self-indulgence, of bigotry, of jealousy, or of 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 and trust, even our most private actions, good or bad, like invisible bacteria inside the blood stream, affect the whole. Everything is known, felt, in one way or another.

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

Ronald Rolheiser, a Roman Catholic priest and member of the Missionary Oblates of Mary Immaculate, is president of the Oblate School of Theology in San Antonio, Texas.

He is a community-builder, lecturer and writer. His books are popular throughout the English-speaking world and his weekly column is carried by more than seventy newspapers worldwide.