8. What fundamental principle underlies Christian unity? Explain.

⁸ Jesus taught his followers a fundamental principle that underlies our unity. “All of you are brothers,” he said. (Read Matthew 23:8, 9.) Of course, one sense in which we are “brothers” is that all of us have descended from Adam. (Acts 17:26) But there is more. Jesus explained that his disciples were brothers and sisters because they recognized Jehovah as their heavenly Father. (Matt. 12:50) In addition, they had become members of one large spiritual family, united by love and faith. Thus in their letters, the apostles often referred to fellow disciples as ‘brothers and sisters.’​—Rom. 1:13; 1 Pet. 2:17; 1 John 3:13.a