I intend to maintain a boundary around my Christian association. That boundary is called, in II John verses 9-10, the doctrine of Christ. Recognizing the boundary markings is an on-going process subject to human imperfection. The process is sometimes called systematic theology. The attempt to mark the boundary sometimes results in a creed or a brief statement of faith.
Within the boundary, I can be on good terms with anyone whom God is.
Within the boundary, I feel closer kinship with someone who is ardent in his attention to God although the lengthy portion of his statement of faith differs from mine, than with someone whose adopted statement of faith is closer to mine yet who is lukewarm in his attention to God.