[la_barba]

>These are not defined in a strict mathematical sense, and they don't actually exist, but the phenomenon certainly does.

That's my point, I'm disputing the central assertion that these phenomenon actually model reality.

>For example, hordes of Twitter users have self-selected who they follow until they're exposed to opinions that agree with their own. This is and has been happening out there, in the real world, to real people.

You can always point to people who unfollow others when exposed to world-view-contradicting opinions. But it hasn't been shown that they always do it, or do it for the same reason in every case. people can and do exhibit contradictory behavior, or have the wrong information, or are simply enjoying the drama, or are trolling, etc. The existence of these and other factors, which are just observations (not models) of human behavior, go against the nice and easy explanations of someone being in a bubble.

We like to put people inside neat little boxes with labels on them. Like you said - " Events occur independently of what names and categories we give them.".

[EForEndeavour]

> But it hasn't been shown that they always do it, or do it for the same reason in every case.

We don't need them to always do it, or for any reason. The fact is that it does happen, as evidenced by, e.g., https://www.cnet.com/news/twitter-echo-chambers-are-very-rea...

[la_barba]

Shockingly, I read the actual study.

"However, as we focused on politically-savvy users on Twitter, the reader should not infer that our observations generalize immediately to other settings, or that echo chamber effects are as pronounced for the general public."

Exactly what I said - " But it hasn't been shown that they always do it, or do it for the same reason in every case."

I don't know why you are pointing to a study that agrees with me.