It has come to my attention that a lot of people are confused as to why God calls certain things sin when they don't directly harm another person.
We know things like lying, murder, adultery, and stealing are immoral. Of course, we can understand why those things are seen as sins because of their harmful nature, but what about things like sex before marriage, substance use, or communicating with the dead?
The most basic answer to that question is that God didn't just call things sin because they harm other people. While it is important to treat others well, it's also important in God's eyes to treat ourselves well.
Starting with premarital sex, the reason this is an issue is because God made sex to be shared between two married people -- because sex signifies the two people becoming one. It's meant to strengthen the bond between husband and wife. Having those relations before marriage can be toxic to everyone involved because if the relationship doesn't work out, the two people could be emotionally impacted. Additionally, should the two conceive a child and then not work out, the child will grow up in a broken home, which often leads to poverty and an emotional impact on the child as well.
Substance use is a little different. It's not necessarily a sin unless substance use becomes substance abuse. For example, having a drink here and there isn't an issue unless it starts being used as a god. That doesn't mean getting down and praying to a bottle of Tequila. Something becomes a false god when it replaces your relationship with God, meaning, if you start drinking away your problems more than taking it to God, there's an issue.
As I've talked about previously in my article 'I Believe In Ghosts, But I Don't Believe In God,' communicating with the dead is not actually communicating with the dead. It's summoning demons, which God doesn't want us to do for obvious reasons.
The bottom line is, God called things sin because they are harmful in some way, whether that be to each other or ourselves.