If the unity of Christians in One Body makes the Church a sign of God in the world, and if men tend unfortunately to conflict and division by reason of their weakness, selfishness and sin, then the will to reconciliation and pardon is necessary if the Church is to make God visible in the world. Nor can this pardon, this communion in forgiveness, remain interior and invisible. It must be clearly manifest. So the mystery of the Church demands that Christians love one another in a visible and concrete way...Christ will not be visible to the world in His Church except in proportion as Christians seek peace and unity with one another and with all men. But since conflict is inevitable, unity cannot be maintained except in great difficulty, with constantly renewed sacrifice, with lucid honety, openness, humility, the readiness to ask forgiveness and to forgive.
Thomas Merton, Seasons of Celebration