Some things can be in the body but not of the body. For example, cancer is in the body, but it rebels against the body's design. The same is true for falsehood in the Church—it may be present, but it doesn’t belong. And that is why God calls His true people to live differently, not just exist visibly. Just as a healthy body fights infection, a healthy Church clings to truth. “Nevertheless the solid foundation of God stands, having this seal: ‘The Lord knows those who are His.’” (2 Timothy 2:19)