Book excerpt: Ideology and Royal Power is a collection of essays describing and assessing the ways in which royal publicists in medieval France conceived the authority of the crown, especially with regard to protecting and defending its Christian subjects from their alleged enemies at home and abroad--corrupt officials, Jews (particularly moneylenders), heretics, and Muslims. A number of the essays also describe the execution of royal policies with respect to these groups and evaluate their impact, both in terms of the groups affected and their influence on further developments in royal ideology. A key figure is that of Louis IX, Saint Louis (r. 1226-1270).