Between the middle of the eleventh century and the time of the Gratians, western Europe saw a remarkable burst of canon law activity. The great number of old collections copied and new collections compiled gives some idea of the appetite for canon law in these times. Starting from very different materials, and with very different problems in mind, prelates from all over Europe engaged anew with the inherited tradition. Recent scholarship has emphasized that “pre-Gratian” collections not only are of interest as preparation for the Decretum Gratiani, but rather shaped the law in remarkably diverse ways. Yet what was “the law”? The collections discussed in the following pages were frequently transmitted together with, and sometimes indistinguishable from, works of sacramental theology, biblical exegesis, penitentials, letters, polemics, sermons, historiography, and cartularies, and there was neither a term nor a definition that would correspond to the modern notion of “canon law.” In practice, canon law was found in biblical precept, patristic writings, synodal acts, papal letters, the legislation of Christian rulers, and other normative texts the Church had come to accept. While new legislation did not fit easily into this concept, between c. 1050 and c. 1150 a very considerable body of “new,” though normally not recent, authorities was introduced, taken from the writings of Augustine, Gregory I, and many other sources, some of which had not been quoted for centuries. This also meant that real or perceived contradictions within the collections increased in our period, and the polemic use of these authorities made the ambiguities of many key texts transparent. However, while all compilers of canon law collections must have been aware of it, attitudes toward this diversity continued to differ.