One particular challenge was the orgiastic Festivals of Mithras and Lupercalia at which Romans let down their hair with a vengeance.
The Christian Church promptly converted the Festival of Mithras into Christmas Day, while the Festival of Lupercalia became St Valentine's Day on 14 February. A debauch was transformed into a safe form of domestic entertainment suitable for everyone.
Ancient history? Not quite. In politically pre-correct days, the wolf whistle was an important part of the vocabulary of any virile, self- respecting building worker. And who doesn't sometimes say "touch wood"?
An exquisite example of this mingling of pagan and Christian is to be found on Guernsey in the Channel Islands. Visit the parish church of St Martin's, a sturdy medieval structure which throws down the gauntlet to passers-by. Are you a Christian? If not, why not? This is muscular Christianity at its most robust.
But not quite. Just outside the churchyard is a seemingly shapeless granite hunk. Look more closely and you can in fact distinguish feminine facial features, hair and a buttoned cape.
This is La Gran' mere du Chimquiere (Cemetery). Several thousand years old, she represents Mother Goddess. For far longer than any recorded history, offerings of flowers and coins were laid at her feet.
But not everyone approved of the Grandmother. One zealous Christian churchwarden who detested this worship of a stone idol tried to cut the figure in two. She defeated his feeble efforts, although a crack is still visible .
The current and informative guide (1988) to St Martin's does not deign to mention the Grandmother. Don't mention it and, hopefully, it will go away.
Mind you, I have a feeling that La Gran' mere will outlive all us puny mortals - and probably Christianity besides.
La Gran' mere du Chimquiere is outside St Martin's church, Guernsey, Channel Islands