ps: You're still right about the incompossibility of particles though. I thought about it a minute and "mutually exclusive" does not sum it up very concisely.

...I've also heard of fermions (though I haven't read extensively and don't understand them at all) -- I just worked myself into a dramatic mood and wanted to make a point which is that "incompossible" has a connotative thrust from the word "possible" embedded in it.