What Is Model-Dependent Realism?

The Grand Design
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Stephen Hawking and Leonard Mlodinow discuss something called "model-dependent realism" in their book The Grand Design. What does this mean? Is it something they made up or do physicists really think about their work this way?

What Is Model-Dependent Realism?

Model-dependent realism is a term for a philosophical approach to scientific inquiry which approaches scientific laws based on how well the model does at describing the physical reality of the situation. Among scientists, this is not a controversial approach.

What is a bit more controversial, is that model-dependent realism does imply that it's somewhat meaningless to discuss the "reality" of the situation. Instead, the only meaningful thing you can talk about is the usefulness of the model.

Many scientists do assume that the physical models which they work with represent the actual underlying physical reality of how nature operates. The problem, of course, is that scientists of the past have also believed this about their own theories and in almost every case their models have been shown by later research to have been incomplete.

Hawking & Mlodinow on Model-Dependent Realism

The phrase "model-dependent realism" appears to have been coined by Stephen Hawking and Leonard Mlodinow in their 2010 book The Grand Design. Here are some quotes related to the concept from that book:

" 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."
"According to model-dependent realism, it is pointless to ask whether a model is real, only whether it agrees with observation. If there are two models that both agree with observation ... then one cannot say that one is more real than another. One can use whichever model is more convenient in the situation under consideration."
"It might be that to describe the universe, we have to employ different theories in different situations. Each theory may have its own version of reality, but according to model-dependent realism, that is acceptable so long as the theories agree in their predictions whenever they overlap, that is, whenever they can both be applied."

Previous Model-Dependent Realism Ideas

Though Hawking & Mlodinow were the first to give it the name model-dependent realism, the idea is far older and has been expressed by previous physicists. One example, in particular, is the Niels Bohr quote:
