THE PICQUIGNY WERE AMONG the very first French aristocrats to commission a private cartulary, but by the fourteenth century such records became more widespread and were even adopted by better-off bourgeois. Private cartularies provided some of the inspiration for a new kind of register that took root among legal professionals and merchants: the liber rationis or livre de raison, kept by the pater familias and often passed on from father to son over several generations. It compiled all manner of material deemed crucial for the management of the family patrimony, from accounts of receipts and disbursements to transcripts of sale deeds, in French, Occitan, or Latin. Indeed, some livres de raison are little more than accounting and patrimonial lists, quite close to private cartularies. However, the inclusion of notes on family events, notably births and marriages, became a defining feature of the genre. The more elaborate livres de raison combine features of family chronicle, account book, and diary; by the end of the fifteenth century more than one such register might be kept by the pater familias. Exceptionally, even a family of illiterate peasants might pay to have their records kept.5 Most of the extant medieval livres de raison are from Limousin and Provence, and it is unlikely that this is merely the effect of the accidents of survival, although the livres’ poorer archival conservation compared to official records explains why only some twenty-odd have been preserved for the period before 1500. Having said this, the medieval livres de raison are something of a textual experiment, unaffected by the constraints of a genre, and as such particularly valuable for the sociocultural historian. By contrast, from the late sixteenth century manuals provided guidelines on keeping a livre de raison, a development that speaks to the standardisation of the genre.

Not all registers that today are grouped under this category were identified by their compilers as livres de raison. This notwithstanding, the name is appropriate because accounting and accountability were crucial in all of them, whether or not the title included the term ratio or raison, in the sense of account or rationale. The term referred both to the ubiquitous accounting of revenues and expenses as well as to the moral accountability of the pater familias towards the family and its posterity.