On the conversion of the European tribes to Christianity the ancient pagan worship was by no means incontinently abandoned. So wholesale had been the conversion of many peoples, whose chiefs or rulers had accepted the new faith on their behalf in a summary manner, that it would be absurd to suppose that any, general acquiescence in the new gospel immediately took place. Indeed, the old beliefs lurked in many neighbourhoods, and even a renaissance of some of them occurred in more than one area. Little by little, however, the Church succeeded in rooting out the public worship of the old pagan deities, but it found it quite impossible to effect an entire reversion of pagan ways, and in the end compromised by exalting the ancient deities to the position of saints in its calendar, either officially, or by usage. In the popular mind, however, these remained as the fairies of woodland and stream, whose worship in a broken-down form still flourished at wayside wells and forest shrines. The Matres, or Mother gods, particularly those of Celtic France and Ireland, the former of which had come to be Romanized, became the bonnes dames of folklore, while the dusii and pilosi, or hairy house-sprites, were so commonly paid tribute that the Church introduced a special question concerning them into its catechism of persons suspected of pagan practice. Nevertheless, the Roman Church, at a somewhat later era, reversed its older and more catholic policy, and sternly set its face against the cultus of paganism in Europe, stigmatizing the several kinds of spirits and derelict gods who were the objects of its worship as demons and devils, whom mankind must eschew with the most pious care if it were to avoid damnation.
~ Lewis Spence