Christianization in the late Roman and early medieval west was a process of slow, incomplete, inconsistent, and sometimes reversible social and religious change. It required not just the conversion of elites, the building of churches, or the founding of bishoprics and monasteries, but the widespread adoption of a Christian self-identity and a Christian system of values, practices, and beliefs. Unlike baptism or “conversion,” which could be imposed from above, the social and religious changes required by christianization could not be put into effect without the consent and participation of local populations. The process of christianization was therefore reciprocal. Although its goals and strategies were established by theologians and its promotion entrusted to lay and clerical elites, its primary actors were the peasants and townspeople who made up local communities and who chose by their very way of life which of the church's teachings to accept, which to reject, and which to adapt for their own ends.

The power of local communities to define their own religious and cultural practices meant that the forms of christianization they chose to enact often differed from the program of christianization proposed by the official church. This occurred primarily because, unlike the traditional religion it sought to replace, Christianity had not arisen from within local culture, but had been imported from the outside and imposed on local populations, especially in the countryside. It was not in its origins a “community” religion, whose boundaries coincided with the boundaries of the local community and whose practices conformed to local traditions, attitudes, and expectations.