Talk:Model-dependent realism

Origin

This article was brought over from Reality and revised. This topic now is introduced there as a sub-topic Reality#Model-dependent realism . John R. Brews 16:40, 12 November 2011 (UTC)

Terminology

The terms "world picture" and "physical theory" are stated by Hawking/Mlodinow to be (math+observations+connecting rules), but they don't always stick to this narrow definition. The term "world picture" is generalized to include any mental construct of reality. They also refer to a "model" as the mathematical part of a theory as distinct from the observational part, but they don't stick to this definition and sometimes use "model" as the same thing as "theory" or "world picture". Hence, quotations from this source can be confusing because one never knows which definition is in use except by reading entire pages for context. John R. Brews 12:26, 13 November 2011 (UTC)

Background

The section Model-dependent realism#Background is very incomplete. Unfortunately, Hawking/Mlodinow make little effort to attach their theory to the very long line of earlier or even contemporary philosophical efforts. The introduction to the book by Cao outlines some of this history and introduces the subject of structural realism. The article on scientific realism the Stanford Encyclopedia of Philosophy lists still more. There is a huge literature, and to place "model-dependent realism" in a proper context requires, in fact, a host of articles on these various topics that can be linked. Otherwise, this article on "model-dependent realism" will become two or three times its present length. John R. Brews 16:35, 13 November 2011 (UTC)

A helpful discussion is found in the article: Mateusz Hohol, Wojciech P. Grygiel. Stephen Hawking's Ontology of Physical Theories. published in: "Philosophy In Science. Methods and Aplications", eds. B. Brożek, J. Mączka, W.P. Grygiel, Copernicus Center Press, Kraków 2011, pp. 105-115.. Retrieved on 2011-11-13. From this article it looks like Hawking has made other efforts to express his views that may be more rigorous and clearer than The Grand Design. John R. Brews 17:08, 13 November 2011 (UTC)

Reviews

The viewpoint of “theory-dependent realism” being espoused in The Grand Design appears to be a kind of half-way house, objective reality being not fully abandoned, but taking different forms depending upon the particular theoretical perspective it is viewed from... Penrose

They advocate "model-dependent realism", which asserts that the "reality" of various elements of nature depends on the model through which one interprets them. This is an interesting approach to ontology, but it won't come as shocking news to philosophers who have thought about the problem. Wall Street Journal

The bulk of reviews focus upon the deliberately controversial elements of this book about God and the validity of M-theory, none of which is important to the concept of "model-dependent realism". One gets the impression that The Grand Design was never a serious attempt at a scholarly position on "reality", but rather a gadfly to get discussion going. John R. Brews 17:08, 13 November 2011 (UTC)

Interpretation of a quote from The Grand Design

A transcription from Talk:Reality. The following quotation is discussed:

There is no picture- or theory-independent concept of reality. Instead we will adopt a view that we will call model-dependent realism: the idea that a physical theory or world picture is a model (generally of a mathematical nature) and a set of rules that connect the elements of the model to observations. This provides a framework with which to interpret modern science.

This is a mixed bag. The first sentence describes their notion of reality. The next sentence is a non-sequitor entirely that introduces the idea of a "physical theory" as a "model and a set of rules that connect the elements of the model to observations". I'd hazard that this statement is an entirely prosaic statement of what most everybody would define as a physical theory. It is simply a definition, and therefore is not attached to the philosopher's "reality". They also introduce here a technical definition for "picture" that is exactly the same thing as a "physical theory". It then defines "model-dependent realism", not as a philosophical position, but as a technical term identical with "physical theory".John R. Brews 16:45, 11 November 2011 (UTC)

Reading it literally, it defines model-dependent realism as "the idea that..." That wording establishes it as "a philosophical position". Anthony.Sebastian 21:09, 12 November 2011 (UTC)

Anthony, that is a misreading. The assertion: "model-dependent realism is the idea that a physical theory or world picture is a model (generally of a mathematical nature) and a set of rules that connect the elements of the model to observations" is not an "idea" at all, whatever they say, because in fact a physical theory is exactly that: "a model (generally of a mathematical nature) and a set of rules that connect the elements of the model to observations". (If you doubt that, consider quantum mechanics as the physical theory consisting of (i) the mathematical model of Hilbert space connected by (ii) rules to the (iii) observations of chemistry.) So their statement is equivalent to the statement "model-dependent realism is the idea that a physical theory is a physical theory", which is an empty remark. To put content into their sentence, it has to be taken as a statement as to what constitutes a physical theory, viz: (model+rules+observations). John R. Brews 05:09, 13 November 2011 (UTC)

Regarding lede sentence as reproduced here

The lede sentence reads:

"In philosophy, model-dependent realism asserts that there is no unique objective reality, but reality consists at least in part of networks of world pictures that connect observations with their explanations or models."

Yet, in reading Hawking/Mlodinow, who introduce 'model-dependent realism', I cannot find such an assertion. I agree they never mention there existing a unique objective reality, but that's not the same.

They do say there can be no picture- or theory independent concept of reality.

They do say, also, that realism is difficult to defend, but that is not their saying there is no unique objective reality. They seem to argue for a model of reality that comprises a network of models, without arguing that model is reality. Anthony.Sebastian 05:02, 17 November 2011 (UTC)

Hi Anthony. I am ready to believe that there are some subtleties that I need some help with. I hope you have the patience to deal with them. Of course, we do not have to come to any resolution of "what is reality" but only to agree upon what Hawking/Mlodinow say about it. I am, unfortunately, unimpressed by these authors ability to use terms consistently or to stick to the same formulation everywhere, so this investigation may lead only to identifying some ambiguities in their presentation. The ultimate objective here is an Introduction that is at least consistent with some form of the Hawking/Mlodinow term "model-dependent realism".

Here is the quote you mention from Hawking/Mlodinow, the lead sentence in the quote above:

There is no picture- or theory-independent concept of reality.

Therefore, in their view, "objective" reality, being a concept of reality, must be a picture- or theory-dependent concept of reality. I would take "picture" to refer to "world picture" and a synonym for "theory", namely the combination (model + rules + observations) in which the "observations" are connected by the "rules" to the "model", the last being perhaps a mathematical structure.

Hawking/Mlodinow also say:

We make models in science, but we also make them in everyday life. model-dependent realism applies not only to scientific models but also to the conscious and subconscious mental models we all create in order to interpret and understand the everyday world. Model-dependent realism corresponds to the way we perceive objects.

I take this as saying that "world pictures" are allowed to encompass as their model component, models more general than scientific models, but they all have the three part structure (model + rules + observations). Combined with the first statement, I am led to understand that "objective" reality, to be allowed as a concept of reality by Hawking/Mlodinow, also is of this form (model + rules + observations).

They say:

We form mental concepts of our home, trees, other people, the electricity that flows from wall sockets, atoms, molecules, and other universes. These mental concepts are the only reality we can know. There is no model-independent test of reality.

Thus, "objective" reality, if it is a concept for Hawking/Mlodinow, can be tested only using a model. Which seems to say that the concept of "objective" reality, if it is a concept for Hawking/Mlodinow, can be approached only through some approximating "world picture" or "theory", because "world pictures" include all constructs that consist of (model+rules+observations).

So I am left with this position on "objective" reality: Our observations, models, and rules connecting them are the only "reality" we can know. If one wishes, one can imagine an objective reality that lies outside this picture, perhaps as some limiting form toward which our "world-pictures" are progressing, but that imagining can never be tested, and all we can know about this "objective" reality gradually emerging from the haze of uncertainty is contained in the best "world picture" we can muster in our particular lifetimes. Inasmuch as the best "world picture" today does not encompass all our observations, and we are forced to use multiple world pictures in some arenas of observation, our best notion of "objective" reality contains ambiguities where our world pictures overlap, and we cannot know how, when, or if these ambiguities will someday be resolved.

This idea of positing "objective" reality as a limiting case, like the limit of a series in mathematics in which each finite sum of terms gets ever closer to the sum to infinity, appears to me to be consistent with Hawking/Mlodinow's model-dependent realism, but to go beyond anything they say. I think they would scoff at this idea because we cannot know anything more about this reality than what is contained in our present best guess at its content, so where the whole process of evolving world-pictures is going is just conjecture, and the process actually may never converge.

Assuming some agreement about this, what is to be done with the sentence:

"In philosophy, model-dependent realism asserts that there is no unique objective reality, but reality consists at least in part of networks of world pictures that connect observations with their explanations or models."

How about this:

"In philosophy, model-dependent realism asserts that all we can know about "objective" reality consists of networks of world pictures that connect observations with their explanations or models."

John R. Brews 12:45, 17 November 2011 (UTC)