LEGAL THERMOMETER Legalism is a terrible threat to the spiritual health of churches and individual Christians. It's the AIDS of the Christian life. There are legalistic churches and grace-based churches. It's important you are able to distinguish between the two. Some people prefer legalist churches, because when they follow the rules it gives them a chance to feel they are doing well as a Christian--especially compared to the other people who aren't keeping the rules as much as they are.