There can be no substitute for the Spirit in producing that unity which will endure all the changes and adversities of life, which will gain the approval of God as realizing His ideal of the Church, and which will savingly influence the world in answer to Christ's prayer for the oneness of all His disciples, "that the world may believe that thou hast sent me." This was the power which conquered the unbelief of the persecutors of the primitive Church. "Behold how these Christians love one another!" This love did not arise from similar intellectual tastes, nor from assent to the same creed, but from the indwelling in their hearts of the same Holy Spirit inciting to mutual love. When love declines through a relaxation of faith and the uprising of selfishness because of the withdrawal of the Spirit from His conscious indwelling, divisions, parties, cliques and sects arise. When we walk along the shore of the sea we observe pools here and there with their inhabitants separated from each other by rocks and stretches of sand, preventing communication between them. This is because the tide is out. But when it again rises and floods the beach the separate pools are swallowed up in the one great ocean. When the Spirit pours floods upon the dry grounds, self is submerged and Christian unity is restored.
— from The Gospel of the Comforter Chapter 20.