Believability

to have confidence in the truth, the existence, or the reliability of something, although without absolute proof that one is right in doing so:
Only if one believes in something can one act purposefully.
to have confidence or faith in the truth of (a positive assertion, story, etc.); give credence to.
to have confidence in the assertions of (a person).
to have a conviction that (a person or thing) is, has been, or will be engaged in a given action or involved in a given situation:
The fugitive is believed to be headed for the Mexican border.
to suppose or assume; understand (usually followed by a noun clause):
I believe that he has left town.
believe in,

to be persuaded of the truth or existence of:
to believe in Zoroastrianism; to believe in ghosts.
to have faith in the reliability, honesty, benevolence, etc., of:
I can help only if you believe in me.

make believe. make1 (def 68).
Contemporary Examples

Delaware’s Affluenza Case Affects Justice, Too Jay Michaelson March 31, 2014

Historical Examples

Herein is Love Reuel L. Howe

verb
(transitive; may take a clause as object) to accept (a statement, supposition, or opinion) as true: I believe God exists
(transitive) to accept the statement or opinion of (a person) as true
(intransitive) foll by in. to be convinced of the truth or existence (of): to believe in fairies
(intransitive) to have religious faith
(when transitive, takes a clause as object) to think, assume, or suppose: I believe that he has left already
(transitive; foll by of; used with can, could, would, etc) to think that someone is able to do (a particular action): I wouldn’t have believed it of him
n.
v.

believe it or not
believe one’s ears