Van Fraassen sobre la metafísica:
Constructive empiricism does not allow an empiricist to project truth onto the unobservable world—which van Fraassen likened to an “insidiously enchanted forest” in Scientific Representation. In the history of science, the enchanted forest has successively been populated with rain gods, musical spheres, phlogiston, ether, multiple universes, big bangs, cosmic inflation, dark matter, dark energy, and singularities. A scientist who believes in the existence of these unobserved entities has wandered into a thicket of metaphysical speculation, and left the realm of science, says van Fraassen.
Science is walled off from metaphysics in van Fraassen’s brand of empiricism by the demand that experimental data must correlate with at least part of the structure of a theoretical model. His bedrock notion of “empirical adequacy” stops at that, forbidding itself to speculate about the (metaphysical) nature of unobserved phenomena. (…)
My main point is that it is practically impossible to describe the chaos of what actually happens in the world. We can construct useful theories or models that are empirically adequate—that tell us something, for instance, about the behavior of what we call electrons, without having to say what an electron is. Parts of a theoretical model can be judged as true or false, based upon the reproducibility of the data. But, to be useful, to be empirically adequate, the data does not have to fit into some overarching theory about the organization of the world. (…)
Science is a large scale, human enterprise and we need boundaries to determine what we can say is true or not about the world around us. Empiricism is a stance, a pragmatic attitude that is self-constrained by what I call “bridled irrationality.” That means that the data itself restricts what is rational to believe about the world; it creates a boundary. (…)
The constructive empiricist says that experimental results and measurement results are the only “real” phenomena that a scientist can witness. The criterion of success is fitting the experimental data into theoretical models that predict the data itself.
By way of example, fitting data about Higgs bosons as imaged by the Large Hadron Collider to the predictions of the Standard Model does not mean the Standard Model is a true theory, just that the Higgs data corresponds to a piece of the theory which was not previously found to be empirically adequate.
The realist disagrees, “No! Empirical adequacy does not go far enough. The criterion of scientific success is that a theory has to be entirely true.” (…)
To be clear, scientists tend to be pragmatists, not philosophers. The takeaway is that if the data conforms to a part of a theoretical scheme that strives to explain the structure of a chair or of the universe, that model can be used as a basis for designing more experiments. If the data does not fit the predictions of the model, then the theory is not useful for science, but fine for metaphysics, if that is what you want to do.