Sin is a religious concept, and it is impossible to understand it it without invoking a religious context. Atheists tend not to believe in it because they recognize that sin is an offense against God, but they don’t believe there is a god (See, for example, this speech by Dan Barker). For those who do believe in God, sin can still be a troubling concept. It seems to denote both individual deeds and a rebellious attitude, acts that nearly anyone would regard as wrong (murder, rape, theft, fraud, perjury) and acts that seem wrong only if you subscribe to a particular set of beliefs (working on Saturday or Sunday, playing card games, cussing, drinking, smoking, and dancing). In the popular—and secular—mind, sin seems to be nearly synonymous with illicit sex or even with ordinary pleasures. So what is sin? And why do Christians make such a big deal out of it?

When I was a child, I thought sin was breaking a commandment. God had a list of rules everyone was supposed to keep. If you broke one of the rules that was a sin. This list of rules, I learned, included the Ten Commandments. To a child, these rules seemed both arbitrary and unnecessary. It made sense that the first rule was to have no other gods. Imagine the confusion that would result from having more than one Rule-maker! But the rest just seemed like nonsense or else so obvious that no one would need to have it written down. Who wants to make graven images? Or take another man’s wife? Or commit murder? The two that made the most sense to me were the requirement to honor my parents and the prohibition against desiring what someone else had. I’ve written elsewhere about this last commandment, but what is especially odd about it is how unenforceable it is. How do you make a charge of coveting stick? The other commandments all enjoin or forbid specific deeds, but this one forbids something that no one around you may even detect. It is one of the earliest indications that God cares as much about why we do what we do as about what we do.

Another thing I thought as a child was that God’s rules are absolutes. In fact, I was very much a rule follower. I was seldom tempted to break rules, and when I did, I was racked with guilt about it until it was discovered and I received punishment or absolution. The existence of a rule was therefore often sufficient to keep me in line. I was surprised, then, when my own children showed no propensity to regard rules in this same way. Most of them would do a quick cost/benefit analysis in their heads before breaking a rule. If the benefit seemed to outweigh the cost, they had no compunction about breaking the rule and no apparent sense of guilt about it. My own natural bent made me a compliant child, but it also set me on a path to becoming a Pharisaical Christian. When you’re good at keeping rules, it’s tempting to think that rule-keeping is sufficient for life. It isn’t.

What I referred to above as “cost/benefit analysis” is a capacity we all have. It is the capacity to decide for ourselves whether a course of action is good or bad. In the myth of the Fall found in Genesis 3, Eve exercises that capacity when she decides “that the fruit of the tree was good for food and pleasing to the eye, and also desirable for gaining wisdom.” Set against her own judgment is the mere prohibition of God, which has nothing to recommend it except God’s power and authority. The serpent even undermines that by accusing God of self-serving motives: “God knows that when you eat from it your eyes will be opened, and you will be like God, knowing good and evil.” God doesn’t want any competition. He only forbade it keep you down. He lied about the whole “you will die” thing. Eve desires good things for herself, and the serpent persuades her that the only thing standing in her way is God’s absurd rule.

This is the normal course of sin. It begins with desire for something God has forbidden. Desire magnifies all the good things that will come and diminishes or eliminates all the potential harms. Then we set our own judgment against God’s and do what we want instead of what we should. Sin begins with disagreement with God.

In orthodox Christian belief God is all-knowing, all-powerful, and present everywhere at once. So his commands are grounded in love and wisdom and strength. But he doesn’t need to have infinite capacities in order to make wise rules. He only needs to be stronger and wiser than you are. Just as good parents who are stronger and wiser than their children make good rules for them to keep them safe and teach them, so God, who is our Parent, makes good rules for us—his children—to protect us and teach us. If we disagree with him, we are always in the wrong. There is something breathtakingly audacious about disagreeing with God, about trying to explain something to him as if he didn’t know, or about thinking we have a perspective he hasn’t considered. It’s like explaining relativity to Einstein. When Abraham dared to do it, he at least showed some trepidation and humility.

Of course, disagreeing with God is not sin; it is only the beginning of sin. For one thing, it is impossible to always agree with God, for to do so, we would have to always believe only what is true and right. Now, each of us thinks that what we believe is true and right. Who would hold on to a belief knowing it to be false or wrong? But we know, since we are human beings with limited perspective, that some of what we believe is not true, even though we don’t know exactly what it is. It is only when we insist on our own way in defiance of God’s command that our disagreement rises to the level of sin. And what is God’s command? He commands us to love him first and foremost and to love our neighbors as ourselves. If our lives are not characterized by loving our neighbors—by sincere respect and affection, wanting what is best for them—then we deceive ourselves when we say we love God.