John, You wrote, regarding emergence: "[ryan's comment] ...is an acceptable beginning from which, hopefully, an explicit (even formal) representation of emergence will come - this is the task before Carmen and me with respect to emergence and completing RedTail Math." I hope we have more conversations abut this topic. You wrote: "I had always assumed that such appeals lie outside the boundaries of legitimate scientific enquiry" They do. However, they are deeply ingrained in many peoples thinking and seem to sneak in at strange times.  I discuss them in psychology (below) but in my experience they are as likely in biology and other "hard" sciences. You wrote: "I was surprised by your inclusion of an injunction against appealing to any higher order principle..." Ok. “principle”, that word works for me. It's when the principle turns into a de-facto "thing" that we get into trouble. I assume that most of what I say below is old-hat to you, but I thought it would be nice for others following the thread… If you and I were out having lunch and you mentioned the idea of someone's "internal working model"  - I would have a way of making sense of what you said and how to put it into some type of real-time behavior and action. We could talk about rep systems, physiological manipulations, the verbal package - whatever - but ulitmately it would relate to some real-time process.  The term "internal working model" in that context is potentially meaningful. It is not an explanation of anything per se but a placeholder in our conversation about something potentially useful and describable. Now, have that same term "internal working model" uttered in the context of a psychologist using it to explain a child's behavior  - "The child does behavior "x" because she has a stable internal working model.” We have just entered la la land, where the noun becomes an explanation. The child does “x” because of “hallucinated entity.” My experience in academia and every day life is that these "explanations" are ubiquitous. I have challenged "scientists" on particular nominalizations with certain success. The group will agree that "yes, we're oversimplifying." Then, two minutes later, another entity will pop up, "mental representations." I can challenge that, and the next thing you know someone brings up "temperament” as an explanation and then later it's a "genetic predisposition" etc. etc.  I do not get the impression that people are aware that they are saying little with their explanatory terms other than, "we simply don't know." The term “mental representation” is a fascinating one, isn’t it? I can use it in the NLP community and it has a certain useful potential. In the world of psychology it (often) becomes an undefined causal entity just like “internal working model” ****BTW – If you want to really have a good laugh, try this on: “Structural Equation Modeling.” Here’s what you do: Ask people a series of questions using some type of a scale with values from one to ten. Let’s say you think the questions are about their “spirituality.” You now have defined a “latent variable.” (Read: hallucinated entity). Of course, you can’t simply study that “variable” by itself; you need to relate it to something. So you ask people a bunch of questions about their “health.” You then create another “latent variable” called “physical functioning.” Now, everybody knows that if you can quantify something it HAS to be REAL and SCIENTIFIC. So you know run mathematical models proving how peoples “high levels” of “spirituality” CAUSES improved “physical functioning.” Sheesh!!! And these people try to tell me that I'M strange. A pleasure - Ryan