But man always has something of sincerity and faithfulness in his nature. Though he lives his life in a changing scene he values steadiness and constancy; the origin of his soul is indeed that one and eternal Spirit which does not change. And it is this human tendency to constancy that has helped to bring about the recognition of the attachment between man and woman, a recognition that has developed into the many and varied institutions of marriage. For the human pair so attached have wished to think of themselves as united in a desire for constancy; and they have also wished others to look upon them as a couple joined in a constant partnership.