The historian Ian Mortimer, in a piece for the guardian yesterday, mentioned "cults of mortification and philosophies of human wretchednes" in the context of the black death.

1348 The worst news year in British history was surely the year that the Black Death reached these shores. The previous year it had struck in Italy, where it killed 40% of some cities' populations in a matter of weeks. Gradually it spread through France, and by September, it had reached the south coast of England. When it was over, according to modern reckoning, more than half the population had been killed. People's confidence in God's providence was another casualty. Cults of mortification and philosophies of human wretchedness began to emerge. Nothing in the last 1,000 years of human experience comes close to the fear and shock of the disease.

What were these cults of mortification and philosophies of human wretchedness?