.But, can anyone figure out what the foundational assumption is upon which the validity of nudge theory as a method rests?

It's very important when thinking through any issue to look for the assumptions upon which it rests. Things we just take for granted, but have never really considered. This is, in my view, one of the most basic qualities of good scientific thinking...to identify assumptions upon which our view of the data, our view of the world rest and then to test those assumptions. All the really great scientists have done this, it's a criterion for great science in a way.

So what is it? What is the basic assumption that must be accepted in order for nudge theory to make sense as a tool an individual, group or society might use to influence the behavior of others? Any ideas?