After readinf some essay on the nature of human fallibility, I was very aware that we are the recipients of a huge amount of discovery over the last century. Medicine exemplifies this. And that has transitioned us from a world in which people's lives were mostly governed by ignorance to one that's constrained by ineptitude. A century ago, we didn't know, for instance, what diseases afflicted us, what their nature really was, or what to do about them. And that has changed.