The "diem" being what Pirsig calls "the cutting edge of Reality".
I am with Das Monde here, in that I see kairos as independent of Rhetoric.
It is the fleeting moment at which we ask our questions of Reality, answer them intuitively by making "Value Judgments", and describe our answers using Rhetoric.
As J A Wheeler said
Reality is defined by the questions you put to it
The difference between approaches was brought home forcibly to me by my current "Technocracy" Diary and observation of the huge difference between the approaches of the US - "Technocracy Incorporated" - and the European - "Network of European Technocrats".
Technocracy being a 1920's and 30's approach to Reality. "Any economic unit can emit money. The serious problem is to get it accepted" Hyman Minsky