The Nature of Unity

What is the basis of Christian unity? Is it belief in the same theory? Is it having the same moral standard? Is it having the same experience? Is it a bond of love and affection? The latter at least seems to have a good Scriptural basis (John 13:34,35; 1 John 3:11-18; 4:7-12). But is there a basis for this love? The unity of believers is ultimately based on who they are in Christ (Romans 12:3-16; 1 Corinthians 12:12-27; Ephesians 4:1-16). This is because Christ has intervened in history and in our lives to make us His children (John 1:12,13; Titus 3:5,6; Colossians 2:13,14). If our unity is based on a philosophy, it would make sense to reject those who had a slightly different theory. If it is based on a moral standard, it would make sense to reject those who had a somewhat different set of rules. If it is based on an experience, it would make sense to reject those who have experienced something different. But if it is based on what Christ did, then we must be careful of rejecting those who have faith in Him even if we do not agree on everything. What do you base unity on?