H. R. Trevor-Roper, The European Witch-Craze of the Sixteenth and
Seventeenth Centuries, NY: Harper and Row (1956 / 1969) pgs 107-108
"Medieval civilization, 'feudal' civilization, was a civilization of
the plains, or at least of the cultivated lands which could sustain the
manor and its organization. In the poor mountain areas, pastoral and individualist,
this 'feudalism' had never fully penetrated thither, or at least it had
not been maintained there in comparable form. Missionaries might have carried
the Gospel into the hills, but a settled Church had not institutionalized
it, and in those closed societies a lightly rooted orthodoxy was easily
turned to heresy or even infidelity. M. Fernand Braudel...has pointed to
isolated mountain societies long untouched, or only superficially touched,
by the religion of state and easily -- if as superficially -- converted
to the...religion of a sudden conqueror.
The mountains, then, are the home not only of sorcery and witchcraft, but
also of primitive religious forms and resistance to new orthodoxies...As
[the Dominicans] carried the gospel of 'feudal' Christian Europe into the
unfeudal, half-Christian societies of the mountains...[they] found that
their success was transitory: that ancient habits of thought reasserted
themselves..."
More material
here
And even this
from the online encyclopedia of the Catholic Church!