This structure, even as far as it has been described already, makes clear at once why the nobility must hold to equality of birth. Already in the constitution of ancient clans, it has been argued, nobles from different clans belonged to a single status group; and although as a rule the clan as such was exogamous (permitting no marriage among its members), that noble stratum always tended to become endogamous, that is, to marry only within itself. If it is the case that nobility presumes solid substance, as it were, with which everyone belonging to it is endowed, and which must be transmitted undiminished to succeeding generations, then every member must have originated in the one circle.

DEFINE: Clarifies the distinction between exogamous clans and endogamous noble status groups, and how this served hereditary purity.

DEFINE: Contrasts exogamous clan structure with the endogamous noble stratum as distinct social units.

Georg Simmel, on individuality and social…, loc. 511