Comment by NoFunPedant

Yes, the Canon Cat had a built-in manual, and I checked the manual quite thoroughly. I learned to use the Cat after a fashion, but even when I understood the Cat a little bit, it still didn't make any sense to me. It especially didn't make sense that there were no separate files and no clear cut way to save your work. By design, the Cat had a single, infinite scrolling text workspace. Documents were separated by a special return code. The user never needed to save a file, because all actions were automatically saved. I now know that the Raskin's theory was that users shouldn't be bothered with thinking about saving or file structure, but at the time it was hugely confusing to me. Most of what the Cat did was invisible to the user. Raskin thought that saved users mental overhead, but all it did was give the user no feedback on what the computer was doing.

The Macintosh, by contrast, was quite transparent to the naive user. It was very easy to understand that if you saved a file, the file was represented by a little picture that you could move to a folder icon or a disk icon. No naive user of the 1980s had any experience with an infinitely long scroll, but the desktop metaphor of file and folder icons was easily understood.

The no-separate-document interface of the Cat was, I think, a huge mistake. That might have been the way Raskin thought people should use computers, but it was a greater conceptual leap than users could easily understand. Non-computer people who were used to typewriters were used to working on separate documents; they thought in terms of writing letters, memos, reports, and manuscripts, and they expected all these documents to stay separate objects.

In the section of The Humane Interface you quote, I think Raskin exaggerates the non-intuitiveness of the mouse. People in the 1980s were familiar with the concept of a pointing device through playing Pong and Centipede. Even before I'd seen a Macintosh in real life, I'd seen the Mac ads and knew what the mouse was supposed to do. As Raskin says, no one needs more than 10 seconds to understand a mouse. It takes a lot more than 10 seconds to understand the Canon Cat.