Creed. (Also, a five letter word for a set of beliefs beginning with "d" is dogma).
The word is credo.
ideology
totemism
religion? Religion is not a word for a set of beliefs but a word for a set of beliefs that explain existence as well as meaning to the universe. Ideology is probably the closest word that explains a set of beliefs probably.
cosset
tenet
Successfully is a 12 letter word with three set of double letters. Stubbornness is another 12 letter word.
set
A creed is a statement of faith or beliefs, coming from the Latin word "credo" meaning "I believe" which is the first word in the Latin version of the Apostles' Creed. There is no "masonic creed" because masons do not have a set of beliefs which are common to all of them. (Every Mason has his own set of beliefs of course) The Masonic Order does have principles on which it is founded as all organizations do, but these are not beliefs.
set, as in set the table
Hester is a Puritan in The Scarlet Letter. The novel is set in the Puritan society of 17th-century Massachusetts, and Hester's actions and beliefs are influenced by the strict religious beliefs of the Puritans.