[Savage Beast]

"what kind of concrete proof could one possibly find?"

You never know.

I remember, back in college, reading Claude Bernard's An Introduction to the Study of Experimental Medicine, first published in 1865, and being amused at his assertion that some disciplines could obviously never be experimental, citing astronomy as an excellent example.

[sopo]

That was about the Jules Verne era wasn’t it ( no, not when we were in college, you likely well after me). Just goes to show some have more imagination than others.