Why would they need to prove something that everyone already believes?

a) to believe implies ones consent to the suggestions of another. How does mass consensus (the many consenting to believe the suggestions of the few) prove reality?

b) what if believing represents ones choice to want or not want the suggestions by others, while ignoring the need to adapt to perceivable?

It's like saying....They don't need to.

a) does saying (to utter in words) represent a need or a want?

b) what comes first...suggested words or perceivable sound?