yes, and when that happens, what you do is c
hange you opinion, not " not have an opinion"

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It's fine to have an opinion, hunch or theory about it or anything, especially when there's a continuous stream of new data coming in. What you and julian are basically saying is
"Bohr should have STFU'd about black holes because we didn't have the Hubble telescope and his opinion upset the establishment" <-that's asinine..
You don't treat said opinion as given fact sure.., but ofcourse you form one.
the role of science is to find the best, most probably answer. Which is in constant flux as the body of evicence grows or shrinks depending on the subject. The capacity for science to change its mind on x subject sais nothing about the state of the answer in the current time frame, and on wether or not its " allowed" to have an opinion on it.
also. the call to " not form an opinion" doesn't come from a place of scientific doctrine in this instance, it comes from a place of fear.