Beliefs are characterized as "true" or "false" in virtue of the truth or falsity of the propositions that are believed. People can believe propositions with varying degrees of conviction, but believing something does not make it so, no matter how hard you believe.

Do beliefs have to be true?

All beliefs are true. No beliefs are wrong, because there can be no universal, certain, objective justification for any belief. All beliefs are based upon cultural influences.

When you believe something is true but its not?

The illusory truth effect (also known as the illusion of truth effect, validity effect, truth effect, or the reiteration effect) is the tendency to believe false information to be correct after repeated exposure.