I've seen several people write about Matz's design principles for Ruby, but I can't find what the man himself wrote. I'd love to read that if someone with better google-fu can dig it up.

Here is some material (some a bit old, last one is a video):

http://linuxdevcenter.com/pub/a/linux/2001/11/29/ruby.html

http://www.artima.com/intv/ruby.html

http://www.youtube.com/watch?v=oEkJvvGEtB4

I'm sure Ruby's design is worth study, and maybe there are things identifiably "japanese" about it. But surely simplicity and symmetry are not among them. It's a very large language, with many non-orthogonal features -- cleaner than perl or C++, but certainly nothing like, say, Lua or Clojure.

Are simplicity and symmetry any more Japanese than they are, say, Greek or Swedish? I think you need to go deeper than that to identify something uniquely Japanese.

I read the two interviews linked by domgblackwell, and it's hard to tell. In the first interview, from 2001, the only design principle he cites is the principle of least surprise. In the 2003 interview, he says he didn't think of that, it was just an observation other people made about Ruby. He talks about the folly of pursuing perfection, "harmonious" rather than orthogonal features, and how the programmer feels when using the language, comfort, joy, etc. That actually sounds pretty Japanese, but the fact that he had a much better articulated design philosophy in 2003 than in 2001 makes me think we will never know what implicit design philosophy guided his creation of Ruby. His purported design philosophy is at least partly a retrospectively constructed just-so story he invented to explain how he was able to come up with Ruby. It makes sense that a Japanese creator, upon discovering that he had created something beautiful, would use familiar concepts to try to explain how he did it.

Possibly. Yukihiro Matsumoto created Ruby which has an essential simplicity even if it can be used in cryptic ways...