heathenism
Heathenism (noun) means the beliefs and way of life associated with heathens.
Etymology
Formed from heathen and -ism, it was coined in the 17th century to replace the then-obsolete heathendom. It is first attested in Francis Bacon's Of the advancement of learning (1605), II. xiv. §9: "The heresy of the Anthropomorphites … and the opinion of Epicurus, answerable to the same in heathenism, who supposed the gods to be in human shape" (OED).