Evidently, the strongest external measure for fixing internally variable relations is law. Examples are the marital form, which unyieldingly confronts changes in personal relationship; the contract between two associates, which continues to divide business profit evenly between them, although one of them does all the work, and the other none; membership in an urban religious community that has become completely alien or antipathetic to the member.

Georg Simmel, on individuality and social…, loc. 779