Re: Rosen & Ashby

again, context is important. If by "material" one means defined on material states alone, then this would be incorrect, because material states are themselves perceptions of a special system property and the "real" or "natural" system is greater than these derived states.

Again, I can only sketch here to what Rosen devotes 9 pages in AS. (Formal systems get a separate lengthy treatment, also.) I will try to summarize, but if you really want the full picture, you'll really have to read AS 2.1. I swear I'm not trying to be cagey, I just can't do justice to his words in this short space! :)

For Rosen, the beginning point of science is "our fundamental awareness of sensory impressions", what he collectively refers to as percepts. He considers it at least plausible that these percepts arise not entirely from within us but, at least in part, are from outside of us - from an external world (equivalently called "material world"). We further associate the presumed sources of those percepts with definite qualities belonging to the external world, and we then make the next step and identify those qualities with the percepts which they generate.

Then, we have relations between these percepts. There relations are not percepts themselves, but rather our mind actively engages in organizing percepts. This active organization process is the process of establishing relations, in the mind, between percepts. However, it also appears plausible that although these relations are creations of the mind that they have some basis in the external world, and we impute these relations back to that external world. These relations thus constitute an indirect form of knowledge of the external world than do the percepts themselves, and he refers to these relations as "working hypotheses" or "models of how the external world is organized."

"Specifically, we shall say that a natural system is a set of qualities, to which definite relations can be imputed. As such, then, a natural system from the outset embodies a mental construct (i.e., a relation established by the mind between percepts) which comprise a hypothesis or model pertaining to the organization of the external world."

So, the only actual empirical 'facts' in this view come from the percepts themselves. It is we who then mentally create the relations between them, as well as having subjectively chosen which percepts will be members of the given "set" of percepts which will form the fundamental empirical basis for any given natural system. A "natural system", either simple or complex, is thus very much an epistemological thing of our own creation, which has referents (i.e., the presumed sources of the percepts) in the material world.

With regard to "material-states": There is no requirement in this view that the organizational relations imputed to the system must be state-based. The idea that state-based descriptions are the only correct and valid way of describing material reality is - in this view - false, and what opens the doorway to allow relational (and other noncomputable) models as equally valid ways of describing material reality.

When you say that "material states are themselves perceptions of a special system property and the "real" or "natural" system is greater than these derived states", how do you know this to be the case? Either this is a metaphysical assertion, or it is a supposition. The empirical basis of a natural system is the percepts. Anything beyond that is hypothesis or supposition. I do agree with your statement (if taken in the form of a supposition) in the following cautious sense: it is highly plausible that the material world (or external world, whichever term you prefer), generically if not universally, has, in some sense, a "greater richness" of qualities and relations than can be discovered in any given selected natural system (or finite set of natural systems), regardless of whether that natural system is simple or complex. But again, I take this as neither empirical fact nor a priori knowledge, but as only plausible supposition about the external world.

If, on the other hand, one means a system with both functional and realized components, that otherwise can be identified by its material states, then yes, that is a natural system, but it involves more than the material states themselves.

Complex systems can behave like, or be percieved as, simple systems. I think this is the context in which this statement is being made. I believe Rosen makes a clear case for mechanisms being artifacts (or sub-systems) of how we view a natural system, and their reality is more that that model indicates. Are they natural systems themselves?

If the supposition is true or even widely true, then it does make it false that the characteristics of these artefacts (mechanisms) represent any fundamental physical principle or limit of the nature of the material world.

These are two very different but entirely compatible statements regarding mechanistic artefacts. The first is that we can define, measure, and create commuting Modeling Relations for, mechanisms. The second is that these artefacts do not thereby tell us anything fundamental about the limits of the nature of material reality.

I do not know if Rosen would consider that supposition (the material world is universally complex) as true, or as most likely true, or as just a supposition. My feeling is he would say: almost certainly true.

You have to keep in mind what comprises any specific natural system: a certain subjectively chosen set of qualities (which are identified with percepts) and the mind-created relations we impute to them. If you then say, "but what about these other qualities (ones that are not within the set of either qualities or relations that comprised the original natural system)?", I think you are then referring to a different natural system since, by definition, changing the set of qualities fundamentally changes what now comprises this natural system (as compared to the original natural system). In short, if you use different sets of qualities, you have different natural systems (where the term natural system is used in the very specific sense in the Rosen quote above). More below...

You have to decide if you want to call sub-systems with more limited properties equivalent to their complex parents or not. Behind every apparent mechanism is a complex system that allows that particular simplification of reality to present itself to us. However, I believe it is a correct interpretation to say that in no case, except our model, is nature truely as simple as a mechanism. To say there is such an example would be to say that the mechanical system was fully closed with respect to larger system interactions (isolated from all complex systems),

I think you are perhaps trying to make the term "natural system" refer to something more objective than it actually is. To point to a rock, for example, and say that as a natural system, it is complex. But, this depends entirely on the choice of subjectively chosen percepts and the relations that will make up that natural system.

If you were to take this rock and use, say, atomic or quantum-level interactions, that for example include impredicative loops of inter-particle forces, as the percepts and relations that comprise the basis of the natural system, then this natural system would clearly be complex. (call this system S2)

[Yes, I am skipping over the fact that a quantum-level interaction cannot be a "sensory impression" proper. That requires the further notion of observable, as well as some other concepts. For our purposes here, 'percept' will suffice as a stand-in.]

However, if I then assert that S1 is "really" S2, what am I doing? I am making a comparison between two subjectively and separately defined epistemological things, S1 and S2. In what sense is S2 any more "real" than S1? I would argue (and I think Rosen would too) that neither is more "real" than the other. Certainly, the referents for S1 and S2 are equally "real". If we were ardent reductionists, then we could, by that belief, assert that S1 can always be unequivocably reduced to S2, and that therefore S2 is not only more precise, but in some sense "more real" than S1. (Certainly, this is part of the attractiveness of a belief in reductionism.)

In general, if reductionism if false, then we cannot make such assertions automatically between any arbitrary S1 and S2 that seem to refer to the "same thing" in the material world. (Think of organisms, for example.) But, in the case of natural systems that are mechanisms, I would agree that we can probably always find some complex natural system which can subsume all the models of the mechanism system into a larger set of models of the corresponding complex natural system. In other words, that the one epistemological thing (S1) is merely a subset of another epistemological thing (S2). It is only in these cases that you could definitively say that a certain system is a "sub-system" of its "complex parent". I am just reluctant to say that this is a priori universally possibly to do, although it seems highly plausible.

An ability to find a "complex parent" to a mechanism does not thereby make mechanisms "imaginary" or "not realizable", to go back to your original remark. We utilize mechanistically defined systems all the time in manufacturing cars and clocks and so on. Mechanisms are eminently practical systems of everyday life. As long as we retain the notion that they are largely, if not entirely, artefactual, and thereby do not indicate any intrinsic physical limit, there is no harm to using them if they serve our purposes.

Again, I don't think the use of language was as precise or consistent as we might like it to be in any single quote for the purpose of making these kinds of distinctions. One has to instead derive meaning from the whole work and allow for some interpretation..

"the use of language"? Rosen's or mine? Don't let my few paragraphs stand in as any kind of adequate proxy for Rosen's many books and papers. His concepts fit together very specifically and have a great deal of supporting discussion and argumentation to them, and I can only refer to little pieces of them at a time.

This is a philosophical escape. If one complex system can fully model another, but by definition no complex system can have a complete "largest" model itself, what is the meaning of the first part of the statement?

This is one of those cases where context is important. "No largest model" is a commonly used (even occasionally by Rosen), albeit somewhat misleading, shorthand version of the more precise phrase "no largest Turing-computable model". So this phrase does not impact on the ability to model a complex system with another complex system.

With this more explicit phrasing it might also now make more sense why the definition of complex system as "A system is complex if it has a nonsimulable model." and "no largest model" (in the more precise form of "no largest Turing-computable model") are closely related. Any number of Turing-computable models can be combined or concatenated into one largest Turing-computable model. Since a complex system will posses at least one non-Turing-computable model, the totality of that system's models cannot be combined or concatenated into one largest Turing-computable model.

The term "describe" loses its meaning, as we would be claiming that something that can't itself be described, can nevertheless be a complete description for something else. Rather esoteric, and the only cases that could work even as a thought exercise would be the (a) entire (imagined) universe being a model for its sub-systems, but the finitude of that isn't even a given, or (b) imagining everything (in its most complex form) as a description for everything else. Neither of these gets us very far.

Instead, what allows for your correcction of my more general statement is a shift in the meaning of the word "describe" with connotations of tangibility, wereas the "correction" re-defines "description" as something intangible (another indescribably complex system), thus invalidating any practical use of the statement.

Well, to me, "to describe" means "to model", with no distinction between model types. So, we are each apparently using the word differently here. I am not sure specifically what you have in mind by "describe" or "practical use" or "tangible". If you mean by those terms essentially that a system will have only "Turing-computable models", then I would agree with you. But, that kind of restriction on "describe" seems to me an artefact of the mechanistic science paradigm.

We have to ask what is a "good enough" statement to afford general understanding in a given context, as there is no absolutely precise syntactic statement of anything (e.g., Rosen's theory) that can be made.