Immanuel Kant defined the very two same things as the noumenal (realism) and the phenomenological (constructivism) already in the 18th century and also saw them as two sides of the same coin. My colleague Jan Söderqvist and I have constructed a similar but more up-to-date opposition of eternalism vs mobilism which we discuss in depth in our forecoming work "The Global Empire" (published in Swedish in 2003). Our point is that there never was any noumenal or phenomenological realities but that the two were always intertwined and that it is within their very confusion, when the two worlds collide, that they both appear to us precisely as eternalistic (the fixed world of phenomena or particles in physics) and mobilistic (the ever-chaning world of noumenal intensities, the equivalent being fields in physics).
For Zarathushtra the two things are of equal importance and striking the balance between the two is what is important for us as human beings. We could even go so far as to say that Ahura is the mobilistic and noumenal character of realism and that Mazda is the eternalistic and phenomenal character of constructivism.
I'll soon come back to this, but it'll take some time. I'm preoccupied
with moving back to Zurich, and the subject is quite tough. At least,
we could say that realism is the idea that there is a mind-independent
reality with its own laws and rules, things that we just run into: the
experience of resistance. Constructivism is its counterpart in the
sense that "those things out there" do not exist by themselves, but
are categorically and linguistically shaped. Now let's combine realism
and constructivism and see them as the two sides of the same coin. :-)
I definitely have to elaborate on this much more. I'll read a bit
about Peircean semiotics (if I find some time) and write a short
summary. What I just wrote above doesn't really deliver.