This is a copy of a post I wrote to leanagile on 6 Oct, 2009. I have copied it here because I feel that it explains my perspective well.
One of the things that has caused me to embrace both Agile and Lean is that they are not closed systems. Each of them (explicitly, I believe) recognizes the need for learning and self-redefinition. As such, I tend to assume that each of them has already absorbed the best of what the other has to offer. In many cases, the two were saying the same thing using different names. In other cases, one or both holds something to be an underlying assumption (I’m thinking the role of People ) that doesn’t get spoken of much, and causes confusion. The primary discussion point of value to me is in understanding how to more properly utilize the thinking patterns coming from both sources. In Lean, I find great value in the attempts to provide a scientific basis for why things work, giving me mental models to help understand future situations. Others perceive this same aspect as a negative, dehumanizing, theorist perspective. I respect that view, even though I don’t agree with it.
I personally perceive that Scrum as a framework has been defined as a closed system. This turned me off on it for a long while until I see people like Tobias Mayer at work… now I question my understanding… thank you Tobias.
I personally perceive that Kanban as a framework has been defined as an open system, but is at risk of being turned into a closed system. I do not wish to see this happen.
Regarding the CAS  aspects of this thread:
I believe it is an incredibly valuable systems-thinking tool and perspective to evaluate what happened in a situation. As such, I believe it is also a valuable tool to predict what may happen in future situations. This puts it in the same bucket as lean, agile, and many of the other tools at our disposal. I wouldn’t “Go CAS” any more than I would “Go Lean” or “Go Agile”, but I will happily add them to the set of lenses I use to understand and inspire in a given situation.
I hope this perspective helps, or at inspires a bit of thought.
 The thread had a deep discussion of the role Complex Adaptive Systems theory could play in Lean transformations.