Mortimer, Ian. Medieval Horizons: Why the Middle Ages Matter (p. 31). RosettaBooks. Kindle Edition.
A more united Church was a more purposeful and powerful organisation. It also grew phenomenally wealthy, expressing its prosperity in the building of tens of thousands of abbeys and parish churches and the foundation of monastic orders. Its wealth was partly a result of the Medieval Warm Period – a period of favourable climate change, discussed in chapter three – but an even more important factor was the scale of the donations it received. The idea of the plenary indulgence, whereby all your sins were forgiven in return for an act of devotion (such as a crusade) had not existed in 1000; now such indulgences were accepted as ways of easing your path to Heaven. Pilgrimages too were phenomenally popular, as ordinary people invoked the healing power of saints and their relics. Whereas once few people had left home for religious purposes, now millions were on the move across Europe, enriching all the churches they visited with their donations. Christendom’s religious horizons had widened and the Church’s penetration into society had deepened, flooding like rainwater after a storm into every private crack and corner of daily life.