As a student, I once... was in a class with... I think it was... I’m trying to remember the professor; it may have been Edward Purcell. But it was... wait a minute. I don’t remember which mathematician it was, but one of the students said: 'Well I understand what one and two and three dimensions are, and… and… I see a little bit of what might be like in four dimensions, but you keep talking about n-dimensional spaces' – Hilbert space has infinite number of dimensions – And the student said: How do you think about these n-dimensional spaces?' The professor stood there for maybe a whole minute and he said: 'Well, you’re not thinking about it the right way. Just think of a particular n.' And then, he went back to... it's a great example of not being helpful. So, that was… I was a young student and I asked Andrew Gleason: 'How do you think of a high dimensional space?' He said: 'Well there are a lot of ways.' So here’s the Society of Mind idea. And he said: 'You can think of a bunch of vectors and just remember that each one is at right angles to all the others.' And then here’s another one, it's… say… whatever… whatever space you’re thinking of, think of it as a surface and ask, what's the solid thing that it’s the surface of? And, if you keep doing that, you keep going in dimensions. And he sort of sat there and mentioned six or seven of these. And I think most students have never had that experience of… of getting that kind of answer where instead of… instead of being told the right way... But the idea… you have to have a lot of vectors and just remember that this one is at right angles to all the others. Well, there’s no way you can imagine that, but… but you can have these little tricks. You can say, oh well I’ll make a… little bundle of this with the other two, that's no problem. I can’t do it with the other three, but who cares. So, that’s the lesson. If somebody says something smart, you should... how did he think of it? Not: How can I repeat that later?