An echo chamber feels like proof. It’s actually just your own voice, bounced back louder.

Hearing the same opinion from ten places feels like ten pieces of evidence, but if they all got it from each other it is one piece repeated. Certainty climbs anyway, because your head counts repetitions rather than independent checks. That is how a group ends up extremely confident about something nobody in it has verified. The confidence is real and the support underneath it is not.

When you are sure about something, try tracing where you first heard it. Ask whether the people who agree arrived from different directions or the same one. One person outside the group who knows the subject is worth the whole chorus.