Ordinary people typically know divine statements through authenticated revelation conveyed by a messenger. Claims about angelic messages likewise require an established route of authority; merely claiming such a message does not yield certainty.
Consensus raises two questions: has the agreement actually been established? and why is it authoritative when established? The former concerns accurate transmission and identification of those whose agreement counts; the latter requires a legal-theological proof.
A corroborated report is supported by additional indicators. Such signs may strengthen credibility, but whether they deliver certainty depends on their quality, not their mere presence.