Are extreme beliefs constitutive of echo chambers, or only typically caused by them? Or are many echo chambers unproblematic, amplifying relatively benign beliefs? This paper details the conceptual relations between echo chambers and extreme beliefs, showing how different conceptual choice-points in how we understand both echo chambers and extreme beliefs affects how we should evaluate, study, and engage with echo chambering groups. We also explore how our theories of extreme beliefs and echo chambers shape social scientific research and contribute in (...) a practical way when treating these phenomena, focusing on examples of climate change scepticism. (shrink)