There is a wide spectrum of levels of consensus and belief, and of the conditions required to achieve them.
For example, a situation may be:
When it is “common knowledge,” accepted on a default basis, and no evidence to the contrary has been presented or recognized.
Certain, True or Proven
When evidence is conclusive or compelling.
In law, when there is a credible and reliable informant who is a witness.
In law, when the summary of evidence is in favor.
When at least one item of direct, verifiable evidence exists.
When consensus-logic arguments “for” are stronger than those “against”.
When evidence and arguments “for” and “against” seem equally plausible.
In law, if the existence of a competing or mutually- exclusive situation is suspected.
In law, when the summary of evidence disfavors it.
When direct or indirect, verifiable evidence is missing.
When arguments “against” are stronger than those “for,” or where consensus logic cannot ascertain consistency or cause and effect.
In law, when not believed, but there is some suggested evidence or argument to support it.
Where no necessary conditions “for” are violated.
In law, when a credible and reliable informant is a witness to direct contrary evidence.
Impossible, False or Disproven
When all necessary conditions for belief are violated or disallowed by conclusive evidence.
Not considered, or there exists some generally-accepted reason to deny it.