I was about to continue the discussion about the topic of the thread, but I just have to say this...
Philosophies, whether western or eastern, can be applied and discussed in extremely wide-ranging contexts and most certainly across cultures. That's the whole point of a "philosophy"... to use it as a tool in analysis, interpretation, debate, etc. It would be a very closed and segregated world if philosophies had to be constrained to the location/culture of their origin. Why shouldn't Chinese philosophy be applied to a western context or vice versa? The world is hopefully a fluid enough place to allow for this. I'd also like to say that I don't think Chinese philosophy has much if anything to do with astrology. I think it's a bit patronizing to Chinese philosophy to make such an assertion.
Further, when discussing a film in terms of interpretation and personal observation there is no reason on earth to feel constrained by what one might feel is the exact intention of the author, either Lee or Proulx (though there's no way to ever really know or prove either author's intention) or to stick to the exact
literal circumstances of the plot as it's spelled out. Literary theory, film theory, art history, etc. are built on these notions. Proulx (for what it's worth) has said that she expects the reader to complete her stories themselves. She's clearly been reading up on Roland Barthes' literary theory in making this statement.
The production of this story/ film is an incredible work of hybridity. This is a story about gay men, written by a straight woman, and in the movie those gay men are portrayed by straight men and while this is a "western" film (in terms of the genre "western") it's directed by an Asian man. Further, the story by the single straight woman was adapted and re-written by a man and a woman for the film. To only think of the story one way (only as about Wyoming or western culture, or the specifics of cowboy culture, or any single context) misses the complexity of the situation. There is no one right answer to these questions or ideas. That's the fun of all these discussion here on the board (at least for me).
I think the application of a concept like yin and yang to the story of Jack and Ennis is absolutely beautiful. The fact that it's a somewhat surprising juxtaposition (perhaps) makes it all the more intriguing I think.
I absolutely agree with what ednbarby said above...
I think the idea of yin and yang (two halves of the same whole, broken down the middle, pushing and pulling at each other) is central to the movie. Along the lines of the Broken In Two discussion, I think the name lends itself to this concept. I know, I know - Annie Proulx has never said this is why she named it what she did, and maybe it wasn't even a conscious choice on her part. Regardless, I think Ang Lee took it and ran. He said he liked "the taste of" the title Brokeback Mountain. I take this to mean that there is a whole lot more meaning there to him than just a quaint name for a particular range.
I'd go so far as to say I think the design of the movie poster hints at the yin and yang idea. The intersecting black and white hats and the opposing yet overlapping profiles subtly suggest... if nothing else... the idea of opposites that rely on one another for definition or that are inextricably linked.