Requirements on Understanding for Software Brains?

Ricky writes: "Until we fully understand how the human brain operates, I don't see how it is possible to download somebody's mind and have it do anything constructive."

Ray Kurzweil believes that we can do it without needing to understand how it works. He thinks that if we can have high-enough resolution scanners, such that we can get an accurate scan of the physical structure of the brain, we can -- basically -- encode and simulate that structure within a computer. Doing this would of course require a suitable understanding of the way the low-level physical structures work, but it would not require an understanding of what the actual neurones and higher-level structures were doing.

Do I think this is possible? I don't know whether it is possible, but I'm not aware of anything that could rule it out. That is, it seems to be a matter of "we'll have to wait and see".