I observed that people use the words mad, crazy, insane and the like to refer above all else to that which they do not understand. It's a mental convenience, a way to draw the line in the sand and declare "no further!". Crazy people are impossible to follow, impossible to understand. You can stand there all day, nodding your head and saying "yeah, I know, I know", but at the end of that long day it's all just gibberish to the listener.
The man stands at the corner, talking to nobody in particular. Half their conversation cannot be heard, and the other half makes no sense in its absence. The man is mad.
The woman jumps from topic to topic, tangent upon tangent, each one so minimally connected to that which came before that she simply cannot be followed. The woman is mad.
The child cries and talks of creatures in their closet, but no creatures can be found. Nevertheless, the child is inconsolable over the nonexistent source of their distress. The child is mad.
The academics stand around and trade jargon with each other. They might as well be making things up as they go along, too proud to ever admit to not understanding each other. The academics are mad.
It's remarkable to think that we find it easier to declare other people "insane" than to admit to any short-coming on our part. I've generally found that everybody is sane and reasonable, but sane and reasonable in their own context, from their own perspectives. When you are so far from those perspectives, when you are so lacking in context, they appear to be insane. When taken to its logical conclusion, I stand watching the homeless man on the street corner, arguing with their personal demons, and I wonder not what madness afflicts them, but what perspective they must be living with.