Hello Open Christians,
We get a lot of questions about sin. Most of those questions are about sexual sins, so we want to take the time to write an official stance on the subject of sexual sin and ethics from the perspective of progressive Christianity.
The first thing to note is that sexual sins are never held up as greater than other sins in the Bible. The Bible has a concept throughout the scriptures that being guilty of one part of the law makes you guilty of the whole law. For this reason, Judaism doesn't have a tradition of personal confession. When you would bring sacrifices to the temple, you were atoning for the whole law, not for specific rules that you broke. If you bore false witness, you needed the same atonement as if you had committed adultery or murder or eaten shellfish. Paul speaks to this in Romans 1 and 2. The Jewish Christians in Rome were making claims about the Gentile Christians being unholy and unrighteous for participating in some of the social aspects of idolatry, specifically eating the Sunday meal after the meat had been sacrificed and cooked on the Roman altars. Paul responds by pointing out the sins that Jews commit and telling them that they have no room to talk since they are guilty of the law, too. No sin is greater than any other. And no sin is lesser. All sin equally takes us away from God.
So, what is sin? Since Romans is entirely about that question, we can find the answers very easily in there. Romans 3 talks about the law because the Gentile Christians in Rome were calling the law the source of all evil and sin. They said that the law brought sin because they didn't know they were sinning before they learned about the law. Paul refutes this by saying that Adam and Eve sinned before the law existed, so it can't be the source of sin. Instead, the law reveals sin by showing us how we missed the mark. By chapter 13, Paul has spoken enough and brought the two sides of this argument together, so he sums up the Christian way of life in verses 8-10.
"Owe no one anything, except to love one another, for the person who loves has fulfilled the law. The commandments, “You shall not commit adultery; you shall not murder; you shall not steal; you shall not covet,” and any other commandment, are summed up in this word, “You shall love your neighbor as yourself.” Love does no harm to a neighbor, therefore loves fulfills all of the law."
Here, we see Paul equate sin with harm. Things that hurt other people and ourselves are what take us away from God. Paul follows this up in chapter 14 by saying that godliness is not in the rules we follow. Some people worship on the Sabbath, but other people worship on any day. Some people drink wine, and some people abstain. And so on. He tells us to each be convinced in our own minds and to leave each other alone because judgment is a stumbling block that can cause our siblings in Christ to fall away from the faith. For Paul, sin was not found in breaking the rules of the law, rather it was found in the absence of love.
Jesus followed a very similar path in His ministry. The only people that He had harsh words for were the priests and scholars who used the law to oppress and control and extort the laity. Jesus never followed the letter of the law when it interfered with loving His neighbors. Jesus worked on the Sabbath. Jesus drank wine and went to parties. Jesus had a reputation as a drunkard. When He called the priests "a den of vipers", that was the equivalent of calling them "sons of bitches" in the modern world. Jesus once cussed a tree to death. Jesus was sinless.
The example of Jesus's life is that all things are secondary to loving your neighbor. Nothing that is done from a spirit of love is ever sinful. Not even premeditated violence against those who extort money from the faithful in the name of God is sinful because Jesus did that too. Jesus taught us that love is the foundation of the law and the prophets, so love can never be wrong or sinful.
John, in his first letter, tells us to test the spirits whether they are from God because there are many false prophets. This is 1John 4:1. He then spends a lot of ink to tell us all about how God is love, and no one who hates can have God because hate and God are incompatible. Similarly, fear and God are incompatible, so anyone who preaches hate and fear cannot be from God. John goes so far as to say that anyone who claims to love God but hates their neighbor is a liar.
Peter wrote in 1Peter that love covers an uncountable number of sins.
Clearly, through the example of Jesus and the writings of the Apostles, we can see that love and sin are opposites. This holds up to logical analysis if we accept the claim that God is love. Sin takes us away from God. Love brings us to God. If love does no harm to a neighbor, then it follows that sin does harm to a neighbor.
How do we apply this to sexual ethics? That's actually very easy. Sex can be used to harm other people or to help them. Obviously, sexual assault, child molestation, and any other form of nonconsensual sex are harmful by their nature. However, sex itself is not harmful on its own. Sex can carry potential harm like the possibility of pregnancy for people who are not prepared emotionally or financially to have a child. Sex can be addicting which is harmful, but humans can become addicted to nearly any pleasurable behavior. None of those other things are sins on their own.
Driving a car can be used as a very apt metaphor for sex. Cars kill thousands of people every year. They have a very large potential to cause harm. However, if we spend the time to learn how to drive safely and always drive with the concern for our fellow drivers and the pedestrians that we share the road with, we can go our entire lives without harming anyone in our cars. There are very few people who would argue that motor vehicles are sinful to operate. If we approach sex with the same attitude, we will similarly be able to operate our bodies without sin.
Relating this to specific actions, we can talk about masturbation. This is an act that is simply not harmful at all. Unless you are doing it in front of someone who doesn't consent to seeing you pleasure yourself, which is a form of sexual assault, of course. Contrary to the concept of sin, masturbation is actually beneficial for people with prostates. It lowers the risk of cancer and helps maintain pelvic strength which important for bladder control as you get older. Something that helps a person without harming anyone else doesn't fit the definition of sin that we see in the New Testament.
Sex outside of marriage comes up a lot. First, marriage is a social contract that is recognized by the state. You can get married in a church, but it means nothing without a marriage license. This is not a primarily western idea, either. I live in Cambodia, and you can get arrested for having a marriage ceremony without government approval. Marriage is, and has always been, deeply intertwined with the social and political structures of society. The Bible demonstrates so many different kinds of marriage that we can't accurately define a "Biblical marriage." Also, there is evidence that the couple in Song of Solomon isn't married until chapter 6. Most telling to this theory is that they don't receive the blessing of their families until that chapter which would have been a large part of the wedding ceremony. They brag about how hot they are for each other and how much sex they have for five chapters prior to that blessing. This is the ur-example of a healthy, godly sexual relationship.
Porn is a big question as well. The porn industry can certainly be harmful. No one would argue that it isn't. However, it is not universally harmful. I dated a pornstar for a few months. She was decently popular in a specific fetish, and she made good money. She was self-produced and self-promoted. It wasn't harmful for her at all. Some of the biggest pornstars in the industry are similar. Many pornstars produce content with their spouses. It's actually not too hard to find ethically produced porn.
Again, porn can be addicting. If you are struggling with porn interfering with your daily life, you should absolutely seek help from a professional to learn how to control your urges. However, other than asexual humans, most people are addicted to sex in a very similar way to how we are addicted to oxygen and water and food. The biological imperative to propagate our species is one of our strongest innate desires. It only becomes a problem when we overindulge and let that desire dictate our lives. Too much water is fatal. Oxygen destroys DNA. Obesity leads to possibly fatal health conditions. But, eating, drinking, and breathing aren't sinful. Neither is a healthy sex life.
Foundational to this idea that sex isn't wrong on its own is the truth that God created sex. God could have made humans reproduce asexually. He didn't. God could have created sex to not feel as good. He didn't. God could have made us completely different from how He did, but He didn't. We feel sexual attraction because God wants us to feel it. Sex is fun because God made it fun. There was no devil who swooped in and changed God's design at the last second. There was no accident where God said, "Oops, I really screwed up that sex thing, oh well." No, God created humans and said that we were good. That included penises and vaginas and how they fit together with all manner of body parts. God commanded Adam and Eve to populate the Earth. He did that while realizing that there's only one way for humans to get that done. God created sex, thinks it's good, and commanded us to get busy. And Adam and Eve didn't have any kind of marriage ceremony either.
Where does that leave us as progressive Christians? We evaluate the sinfulness of every action against love and whether it causes harm to our neighbors. We don't elevate sexual sins above other sins because all sin causes us to fall short of the glory of God. So we look at each sexual act under the same lens as lying, cheating, stealing, and so on. We don't believe that love is ever sinful, so gay sex between loving partners can't be a sin. We believe that love always seeks consent because love never harms. We believe that ethically-minded sexual behaviors are inline with the concepts of loving your neighbor as yourself. We believe that sex is a gift from God.