He was an intuitive mathematician. Didn't... couldn’t do any real mathematics, but he guessed...  he was remarkably good at guessing... guessing what might be true. So, there were a few of us who hung around and proved that what he conjectured was right, but... but I have ghosts because of this. So, if I’m stuck on a problem, sometimes I imagine Andrew Gleason saying: 'Well, you’re wasting your time.  Try something else.' Or I have the... I used to hang around John Cage a little bit and... he’s one of my ghosts, I didn’t know him that well, but if I’m doing something, he’s saying: 'That’s too pretentious.' And sometimes I have the voice of McCulloch saying: 'You should... you should make that more grand. It's really... show why it’s important.' So, McCulloch is one of the people who watches me when I write and says that's... either, that’s too pretentious, or, not pretentious enough but... do you have people like that? I think I sometimes say... it's a joke between me and my friend Vitek, we say... he made this up. Which was: What would Feynman do? Exactly. For mathematics I say, what would Gleason do? And... that’s the advice I give students, but they don’t listen much. And that's... if you’re talking to someone like Feynman or Gleason who says something, what the students do is they take notes and write it down. And they try to remember what he said, but what you should say is, how did he think of that?  And then, you can go and ask him.