There's also the Null Hypothesis: that it isn't what was (seen to be) "working". I went so far as to use quotes, because, how do we even know what "not working

There's also the Null Hypothesis: that it isn't what was (seen to be) "working". I went so far as to use quotes, because, how do we even know what "not working" would have looked like? If the Null Hypothesis were false, might he population actually have been, overall, healthier without all this "medicine"?