I believe the question here makes assumptions which invalidate the endeavor. You assume that "nothing" is something which exists; without getting into the philosophical and formal approaches to the concept of "nothingness," this is patently contradictory. Taking from the discussion [here](http://en.wikipedia.org/wiki/Nothing), one may propose that "nothing" can be defined as "not anything," or in a very rough sense, the negation of all that there is (minus the contradictory negating of course; refer to the history of modern set theories and formal logic to see what I mean). So, in the strictest sense, it is not possible to subtract not anything from *any* set as subtraction is a binary operation; i.e., what you are asking equivalent to asking, for example, "58 - ". Doesn't hold, does it? At any rate, I hope I've addressed your concern here.