The most important thing I got from Butler and Chuck's talk today is that's not enough to have an idea and it's not enough to actually go out and build it.
One of the things that Butler specially and Bob Tailor had decided was to be conservative.
PARC is always talked about as the forefront of technology and everything else, but in fact was, part of what was done at PARC I think was a reaction against the bubblegum kind of technology that we all used to build in the 60s that could barely work for the single person who had designed and build it, Butler and Bob and Chuck did not want to have that happen again.
So we have to me two interesting streams at PARC one was kind of a humbleness which I'm sure no Xerox executive will ever recognise that word as applied to us but in fact it was saying "we can't do everything, we have to hold some limits in order be able to replicate this systems", and then there's the incredible arrogance on the others side of saying BUT we have to be able to build every piece of hardware and software in order to control our own destiny.
So you have these two things, the conservative attitude and then pulling out all the stops once the idea that you had to replicate the systems was made, I think that to me sums up why PARC worked.
The other talk Alan Kay mentions is Chuck Thacker, "Personal Distributed Computing—The Alto and Ethernet Hardware"
A Playlist with more talks from the conference: ACM Conference on the History of Personal Workstations