I have been thinking about a variation of this statement for a few weeks because it serves as a premise for something I am currently writing.
briefly, I think that rhetoric (the field of study rather than the "art of discourse" exclusively) ultimately has nothing to do with the concrete world, but it does require a particular image of our lived reality--a snapshot, perhaps--before the rhetorical act can begin. from this snapshot of reality, we can then use language to reshape events that occurred prior to that image (revisionist history, hindsight, assorted epistemologies, etc.) or construct a possible reality informed by that image (political discourse is likely the best example). neither exists in the physical world, but we can imagine a reality in which they can exist. a potential issue arising from this is that some physical reality must exist before the picture can be taken; but once taken, it ceases to be an objective view of the world because it is now framed by...well, take your metaphorical pick. the camera, the framing/composition of said image, someone's POV, language. ultimately, physical reality becomes subservient to our experienced/perceived reality and all the baggage that goes along with it. and for me, heaviest of all is language.
basically I like this idea and think there's lots of fun implications to it.