abiogenist - a believer in abiogenesis

apostle - an ardent early supporter of a cause or reform; "an apostle of revolution"

colonialist - a believer in colonialism

Confucian - a believer in the teachings of Confucius

imperialist - a believer in imperialism

Malthusian - a believer in Malthusian theory

admirer, booster, protagonist, supporter, champion, friend - a person who backs a politician or a team etc.; "all their supporters came out for the game"; "they are friends of the library"

vitalist - one who believes in vitalism

denomination - a group of religious congregations having its own organization and a distinctive faith

religionist, religious person - a person who manifests devotion to a deity

theist - one who believes in the existence of a god or gods

devil worshiper - someone who worships devils

monotheist - a believer in one god

mystic, religious mystic - someone who believes in the existence of realities beyond human comprehension

numerologist - a believer in numerology

pantheist - someone who believes that God and the universe are the same

pilgrim - some one who journeys to a sacred place as an act of religious devotion

sun worshiper - someone who worships the sun

theosophist - a believer in theosophy