Don Carson teaches on 1 John 4:1–5:4, exploring the themes of truth and love and the importance of spiritual discernment. He encourages Christians to display God's character and nature through loving others and obeying God's commands, and he cautions us to distinguish between genuine spirituality and deceptive spiritual experiences. First John 4:1–3 is a crucial truth test, warning against false prophets and demonstrating the importance of acknowledging Christ's humanity.