An advertising agency wrote seeking our ministry's business: "Let's face it: appearance is everything. Let us help you enhance your image."

My first thought was This agency must not realize they are dealing with a Christian organization.

But then it occurred to me that this is precisely the impression many unbelievers must get from the state of evangelical Christianity today: Appearance is everything. Truth and reality often take a back seat to image.

This sort of mentality has long been a plague on the church, but in recent years it has reached epidemic proportions. Sadly enough, Christian leaders are frequently the most image-conscious of all. And whole churches are being built on the philosophy that image is everything, while truth is something that must be downplayed or camouflaged so that the church can appear in more appealing dress.

In order to achieve a friendly, non-confrontive image, many churches forego the practice of church discipline altogether, lest the all-important image be tarnished. Sin in the body is tolerable as long as the carefully polished veneer remains in place.

Worst of all, this attitude is all too pervasive at the individual level. Many modern Christians live their lives as if a pretense of righteousness were as good as the real thing.

That is precisely the error committed by the Pharisees of Jesus' day. They had externalized the demands of the law. And many of them lived as if external obedience to the law fulfilled all the demands of divine righteousness.

Again and again Christ rebuked the Pharisees for their fastidious observance of the external, ceremonial law—married with a wanton neglect of the law's moral requirements. The Pharisees' teaching had placed so much emphasis on external appearance that it was commonly believed evil thoughts were not really sinful, as long as they did not become acts. The Pharisees and their followers became utterly preoccupied with appearing to be righteous. Yet they were all too willing to tolerate the grossest sins of the heart. That is why Jesus likened them to whitewashed tombs, spotless on the outside, but filled with corruption and defilement on the inside.

The notion that morality is merely external underlies all forms of hypocrisy. It is the very error Jesus decried in His exposition of the moral law in the Sermon on the Mount. The central lesson He underscored was this: External appearance is not what matters most. The proper focus of the moral law is the heart, not merely external behavior.

Jesus' exposition of the law is a devastating blow against the lie that image is everything. Our Lord taught repeatedly that sin bottled up on the inside, concealed from everyone else's view, carries the very same guilt as sin that manifests itself in the worst forms of ungodly behavior. Those who hate others are as guilty as those who act out their hatred; and those who indulge in private lusts are as culpable as wanton adulterers (Matthew 5:21-30).

So Christians are not to think of secret sins as somehow less serious and more respectable than the sins everyone sees. Here are three reasons secret sin is especially abhorrent:

1. The heart is open and laid bare before God.

Scripture tells us that nothing is hidden from the Lord’s sight, “but all things are open and laid bare to the eyes of Him with whom we have to do” (Hebrews 4:13). No sin—not even a whispered curse or a fleeting evil thought—is hidden from the view of God. In fact, if we realized that God himself is the only audience for such secret sins, we might be less inclined to write them off so lightly.

The Bible declares that God will one day judge the secrets of every heart (Romans 2:16). He "will bring every act to judgment, everything which is hidden, whether it is good or evil" (Ecclesiastes 12:14).

Not only that, secret sins will not remain secret. "The Lord [will] bring to light the things hidden in the darkness" (1 Corinthians 4:5). Jesus said, "There is nothing covered up that will not be revealed, and hidden that will not be known. Accordingly, whatever you have said in the dark shall be heard in the light, and what you have whispered in the inner rooms shall be proclaimed upon the housetops" (Luke 12:2-3). Those who think they can evade shame by sinning in secret will discover one day that open disclosure of their secrets before the very throne of God is the worst shame of all.

It is folly to think we can mitigate our sin by keeping it secret. It is double folly to tell ourselves that we are better than others because we sin in private rather than in public. And it is the very height of folly to convince ourselves that we can get away with sin by covering it up. "He who conceals his transgressions will not prosper" (Proverbs 28:13).

All sin is an assault against our holy God, whether it is done in public or in secret. And God, who beholds even the innermost secrets of the heart, sees our sin clearly, no matter how well we think we have covered it.

2. The heart is the root of all sin.

When Jesus said hatred carries the same kind of guilt as murder, and lust is the very essence of adultery, He was not suggesting that there is no difference in degree between sin that takes place in the mind and sin that is acted out. Scripture does not teach that all sins are of equal enormity. That some sins are worse than others is both patently obvious and thoroughly biblical. Scripture plainly teaches this, for example, when it tells us the sin of Judas was greater than the sin of Pilate (John 19:11).

But in His Sermon on the Mount Jesus was pointing out that anger arises from the same moral defect as murder; and the one who lusts suffers from the same character flaw as the adulterer. Furthermore, those who engage in thought-sins are guilty of violating the same moral precepts as those who commit acts of murder and adultery.

In other words, secret sins of the heart are morally tantamount to the worst kind of evil deeds—even if they are sins of a lesser degree. The lustful person has no right to feel morally superior to a wanton fornicator. The fact that she indulges in lust is proof she is capable of immoral acts as well. The fact that he hates his brother shows that he has murder lurking in his heart. All sin, regardless of degree or extent, springs forth from the same wicked intentions and desires of the heart.

Christ was teaching us to view our own secret sins with the same moral revulsion we feel for wanton acts of public sin.

3. The heart is the true measure of the person.

The Lord isn’t fooled by façades or disguises—He “sees not as man sees, for man looks at the outward appearance, but the Lord looks at the heart" (1 Samuel 16:7). No amount of posturing or performance can conceal the true nature of a heart given over to secret sin.

In fact, those who sin secretly actually intensify their guilt, because they add the sin of hypocrisy to their offense. Hypocrisy is a grave sin in its own right. It also produces an especially debilitating kind of guilt, because by definition hypocrisy entails the concealing of sin. And the only remedy for any kind of sin involves uncovering our guilt through sincere confession.

Hypocrisy therefore permeates the soul with a predisposition against genuine repentance. That is why Jesus referred to hypocrisy as "the leaven of the Pharisees" (Luke 12:1).

Hypocrisy also works directly against the conscience. There's no way to be hypocritical without some searing of the conscience. Therefore hypocrisy inevitably makes way for the most vile, soul-coloring, character-damaging secret sins. Thus hypocrisy compounds itself, just like leaven.

Beware that sort of leaven. An ungodly culture tells us that appearances are everything. Don't buy that lie.

The truth is that our secret life is the real litmus test of our character: "As he thinks within himself, so he is" (Proverbs 23:7). Do you want to know who you really are? Take a hard look at your private life—especially your innermost thoughts. Gaze into the mirror of God's Word, and allow it to disclose and correct the real thoughts and motives of your heart.