An important philosophical idea during the enlightenment was that

dirty, contaminated water

contaminated food,

chlostrophobic living spaces,

mice infestation,

etc,

a) hostility to or prejudice against jews.

b) the holocaust, also referred to as the shoah, was a genocide during world war ii in which nazi germany, aided by its collaborators, systematically murdered approximately 6 million european jews             , around two-thirds of the jewish population of europe, between 1941 and 1945.