If declarative programming is possible at the instruction/action level?
Machine code is imperative, not declarative, so if you want your code to execute on a conventional CPU, at some point there needs to be some code that converts the declarative program to imperative style (e.g., a compiler), and at least some of that code needs to be written imperatively (because at least some of it needs to be written in machine code).  It can't be turtles all the way down.