2) I guess the ones that are based on subjective interpretation instead of objective fact (whatever that is today). There is a book called "How we know what isn't so" (https://www.amazon.com/How-Know-What-Isnt-Fallibility-dp-002...), and it talks a fair amount about humans can clash by developing different interpretations of reality that they think are really real. I guess this isn't "touchy-feely"; I guess it is just that the reason I got into engineering is that machines are a lot more predictable and understandable than humans (to me). I did not mean to denigrate anyone's choice of book; I just didn't have a better term at hand (I still don't!)