Plus the methodology. There’s an idea of actively seeking out research contrary to one’s hypothesis, this helps circumvent the confirmation bias of only looking for things that support a hypothesis and ignoring anything contradictory. It can be healthy to find and consider dissenting opinions.

Another fundamental issue is people using different meanings for similar words. Someone with a strong understanding of scientific method will say things like “I believe” or “studies show”, while someone else will say things like “This is” or “we know”. Colloquially the latter is stronger language conveying more confidence, but the former is more likely to be evidence based. “Theory” is used colloquially the way a scientist would use “hypothesis”. People will say “I have a theory”, that’s only a few sentences and doesn’t make any reliable predictions, the put down an actual theory backed by years of supporting evidence and peer review as “just a theory”.