What is sin? It’s probably not at the top of the list of what most people want to talk about, but sin—and how it is defined—affects almost everything. Understanding what sin is, what it is not, and how to overcome it makes much of life fall into place. Far from being a dusty, dry, boring subject, the topic of sin and gaining a true understanding of it is at the center of understanding life itself.

Isaiah 11:9 reads that “the earth shall be full of the knowledge of the Lord as the waters cover the sea.” One of the keys to the joyful new world Christ will establish will be the knowledge of God spreading to all corners of the earth. But this knowledge is not simply about better agricultural practices or more accurate science. It will include a true understanding of sin. A knowledge of what sin truly is—and what it is not—will prove to be a vital component of all the wonders to come in the Millennium!

Just what is sin?

Mankind Can’t Seem to Agree on What Sin Is

With the sole exception of Jesus Christ, every human who has ever lived has sinned (Romans 3:23). We all have earned what’s called “the wages of sin”—death (Romans 6:23). In 1 John 1:8–9, we read that if we claim to be without sin, we deceive ourselves, but if we confess and forsake our sins, “He is faithful and just to forgive us our sins.” How we live matters. But we can have hope because of Jesus’ sacrifice. He died for everyone because of His love for all mankind. “But God demonstrates His own love toward us, in that while we were still sinners, Christ died for us” (Romans 5:8). “For God so loved the world that He gave His only begotten Son, that whoever believes in Him should not perish but have everlasting life” (John 3:16).

It is crucial to understand that all people need to have their sins covered and forgiven, and God is willing to do that because of His great love for mankind. The Apostle Paul makes clear that “all have sinned and fall short of the glory of God” (Romans 3:23). John gives us no room to deny it, telling us, “If we say that we have no sin, we deceive ourselves, and the truth is not in us” (1 John 1:8).

But what is sin? How should it be defined?

In our world today, there is widespread confusion and disagreement regarding acceptable moral behavior. A 2015 Pew Research report demonstrated how confused the American public is about right and wrong. When asked which behaviors they considered sinful, 22 percent of the American population said that abortion is not a sin, 29 percent said that homosexual behavior is not a sin, and 40 percent of people surveyed said that living with a romantic partner outside of marriage is not a sin. On the other hand, 19 percent of people surveyed said that using energy without considering the environment is a sin!

Why is there so much disparity and confusion about what defines sin? Maybe it’s best summed up by the final verse of the book of Judges: “In those days there was no king in Israel; everyone did what was right in his own eyes” (Judges 21:25). Perhaps looking at how some people define sin can shed some light on the matter.

Some people who profess atheism might say that good behavior is simply defined as being good to all, doing what is right for you, and avoiding hurting anyone if you can. Sounds good, doesn’t it? On the surface, it does. It even sounds similar to God’s command to love our neighbor as ourselves. But what is wrong with that philosophy? Is it a sufficient guide for how we should conduct ourselves?

What if what I think is good contradicts what you think is good? What if our ideas clash? Today, for instance, it is not uncommon for someone to “fall in love” with another person who is already married and feel there is no choice but to pursue that relationship—even if a marriage or family is destroyed. Who should bear the burden of pain in this case—should the other spouse and any children in the family, or the new “couple,” each of whom has suddenly “found” his or her “soulmate” after one of them was already married? How is that determined? How does human reason alone guarantee what is “good” in such a situation, when pain or hurt will result no matter which path is taken?

What about professing Christians? How do they define sin? In general, many well-meaning mainstream Christians will define sin as “not loving others or not keeping the New Testament covenant.” What’s the problem with that? What does “love” really mean? And what does the “New Testament covenant” say? Many will quote Paul, who said that “love is the fulfillment of the law” (Romans 13:10), believing it supports their belief that love has superseded law to define what appropriate behavior is. While most will say the Ten Commandments are good, when pressed many will confess they do not believe a life of obedience to those commandments is in any way required for eternal life. Instead, such a notion is set aside in favor of a nebulous requirement of “love.” However, Jesus said, “If you love Me, keep My commandments” (John 14:15). To which commandments was Jesus referring? He said elsewhere, “If you want to enter into life, keep the commandments” (Matthew 19:17), and then proceeded to list several of the Ten Commandments. Later, James explained that compromising on one law breaks them all (James 2:10).

Did you know that more than a hundred years ago, some social commentators in the United States were very concerned about the effects of baseball’s growing popularity? They were concerned that Sunday-afternoon baseball games were drawing professing Christians away from keeping “the Sabbath,” and so eroding their faith. This controversy is outlined in a book written in 1900 by Abram Herbert Lewis, titled Swift Decadence of Sunday, What Next?

But what was really happening? Protestant leaders had long before eroded the Ten Commandments by perpetuating the false doctrine of keeping Sunday instead of the true seventh-day Sabbath. They held to their position by saying the law was “done away.” However, once you do away with one law, what is keeping you from doing away with another, and another, and yet another? One compromise leads to more compromising. Once religious leaders changed the definition of “sin” to a vague “lack of love,” their moral argument was doomed. The current climate of “anything goes” is the result.

Sin Is the Transgression of God’s Law

The common denominator for all the wrong approaches to sin is that they are based on human reasoning. Can we rely on human reasoning to determine spiritual truth? No. As Solomon said, “There is a way that seems right to a man, but its end is the way of death” (Proverbs 14:12). The only valid definition of sin is the one that came from the One who created us. He inspired the Apostle John to write, “Whosoever commits sin transgresses also the law: for sin is the transgression of the law” (1 John 3:4, Jubilee Bible 2000). That is God’s own definition of sin.

Where does relying on nothing more than human reasoning about sin lead us? If you want to know, just look around, because that approach is precisely what has produced the society we have. Is our society today, by and large, one of order or disorder—harmony or chaos—violence or peace? Our current society is the result of an overdependence on purely human reasoning about such things—reasoning that man, by himself, cannot truly separate from the deceptions of Satan the devil.

Unlike man’s personal ideas about what sin is, God’s definition is not arbitrary. His commandments are not only reflections of His perfect and unchangeable character—they are also designed for our good. Notice what Moses told the ancient Israelites: “You shall therefore keep His statutes and His commandments which I command you today, that it may go well with you and with your children after you, and that you may prolong your days in the land which the Lord your God is giving you for all time” (Deuteronomy 4:40). That same idea is repeated later: “And the Lord commanded us to observe all these statutes, to fear the Lord our God, for our good always, that He might preserve us alive, as it is this day” (Deuteronomy 6:24). His laws—not our own ideas of what is good—will keep us from reaping sin’s consequences and will reward us with what is truly good.

With the Holy Spirit, We Can Know What Sin Is

God firmly warns His people to come out of Babylon (Revelation 18:4). The Greek word Babylon (Babel in Hebrew) means confusion, and when we ignore God’s definition of right and wrong, mankind’s ways do end in confusion—so much so that society has lost the ability to think clearly and soundly. The Bible has to be our guide concerning what sin is—not our opinions or feelings.

God, not mankind, is the one who decides what sin is and is not. “I would not have known sin except through the law. For I would not have known covetousness unless the law had said, ‘You shall not covet’” (Romans 7:7). It is immensely important to understand and keep the law, because the law defines sin.

Jesus Christ is the standard (Ephesians 4:13). Only His living in a Christian through the Holy Spirit can help human beings keep God’s law the way the Eternal intended it to be kept. Jesus kept His Father’s law perfectly in every way—and He will help us keep it, as well. By itself, mankind can never keep it perfectly, as the history of Israel teaches us. However, when people sin, God, out of His perfect love, covers their sins when they repent and seek to love God by keeping His commandments with His help (1 John 5:3).

The world is deceived. Whether atheists, mainstream Christians, or anyone in between, most do not truly understand what sin is—but we can know. Through the understanding given only through God’s Spirit, we don’t have to be confused: Sin is the transgression of God’s law. Through Jesus Christ, we have forgiveness and mercy when we do sin. Through His Spirit, He will even give us the power to resist and overcome sin—something every one of us desperately needs.