As nouns the difference between pietism and deism
is that pietism
is (christianity|often capitalized) a movement in the lutheran church in the 17th and 18th centuries, calling for a return to practical and devout christianity while deism
is a philosophical belief in the existence of a god (or goddess) knowable through human reason; especially, a belief in a creator god unaccompanied by any belief in supernatural phenomena or specific religious doctrines.
(Christianity, often capitalized) A movement in the Lutheran church in the 17th and 18th centuries, calling for a return to practical and devout Christianity.
*2009 , (Diarmaid MacCulloch), A History of Christianity , Penguin 2010, p. 739:
*:From its earliest days, Pietism was intimately bound up with education.
The religious philosophy and movement that became prominent in England, France, and the United States in the 17th and 18th centuries that rejects supernatural events (prophecy, miracles) and divine revelation prominent in organized religion, along with holy books and revealed religions that assert the existence of such things.
Reference to the 17th and 18th century movement is more frequently capitalized, while reference to the general philosophy or belief is more frequently not capitalized.