THE establishment of the heritability of fiefs was numbered by Montesquieu among the constituents of ‘feudal government’ as opposed to the ‘political government’ of Carolingian times. This classification is correct, though it should be borne in mind that, in the literal sense, the term ‘heritability’ is inexact. Possession of the fief was never transmitted automatically by the death of the previous holder. But, except in certain rigorously prescribed circumstances, the lord had no power to refuse investiture to the natural heir, provided the latter did homage beforehand. The triumph of heritability in this sense was the triumph of social forces over an obsolescent right. In order to understand the reasons for this it is essential to form an idea of the attitude of the parties concerned. We shall confine our enquiry to the simplest case: that in which the vassal left only one son.