lundi 22 août 2016

Empirical Adequacy: a Proposal

In the last post, I criticised van Fraassen's definition of empirical adequacy. According to van Fraassen, a theory is empirically adequate if it has at least one model such that all observable phenomena fit inside (they correspond to the empirical substructures of the model). My criticisms were the following: it rests on a problematic distinction between observable and unobservable, it does not take into account interventions and manipulations, which are central in scientific experimentation, and it refers to an hypothetical model of the universe, which is unnecessary and disconnected from scientific practice.

Can we do better? I think we can if we directly refer to scientific experimentation instead of coming up with an abstract reconstruction of empirical adequacy. Empirical adequacy should simply be framed in terms of the good predictions of models when they apply to various situations. Thus I suggest the following definition:

A theory is empirically adequate exactly if, for all its models, and for all concrete situations in the world, if the model applies to the situation, then its predictions are correct.

Here it is: that's a pretty simple definition. Now, of course, I need to expand a bit what all this means. This is the aim of the present post. But let me begin with an illustration.

Take as a concrete situation the evolution of the solar system during a certain period of time. A Newtonian model of the solar system applies to this situation if it correctly describes the planets and the sun, with their respective initial positions and masses. It makes good predictions if the evolution of the position of planets in the model correspond to the positions that we could observe in this situation. If this is so, then our model of the solar system is empirically adequate for this situation. If all models of the theory that we could apply in the world are empirically adequate for all situations to which they apply in the world, then our theory is empirically adequate.

I will now explain in more details what I mean by situation, application and prediction.

samedi 20 août 2016

What is Empirical Adequacy? Against Observability and the Model of the Universe.

In the last post, I explained how I conceive of physical theories: roughly, a vocabulary and axioms, from which we build models applicable to particular types of situations. Models can be mapped to concrete situations in the world, and we can compare their predictions to data models extracted from these situations. From this picture, we can ask: what is it, for a theory, to be empirically adequate?

Van Fraassen, who is one of the main contemporary defenders of empiricism, proposes a definition of empirical adequacy which is the following:

"A theory is empirically adequate exactly if what it says about the observable things and events in this world, is true—exactly if it ‘saves the phenomena’. A little more precisely: such a theory has at least one model that all the actual phenomena fit inside. I must emphasize that this refers to all the phenomena; these are not exhausted by those actually observed, nor even by those observed at some time, whether past, present, or future."

This definition dates back to his 1980 book "the scientific image" (You can find a similar one in a footnote of his 1989 "laws and symmetry"). What he means by "fit inside" is explicated later in the book in terms of isomorphism between data models and the "empirical substructures" of theoretical models. I think it's not the right way to understand empirical adequacy for several reasons, and although his notion of "fit inside" was challenged by some authors, who proposed more sophisticated accounts, this is hardly my main point of contention.

dimanche 7 août 2016

How do scientific theories represent the world? The semantic view reconsidered.

Before to wonder whether scientific theories are correct description of reality, or if they only "save the phenomena", one should better be clear about what scientific theories are, and how they are confronted to experience. In this post, I discuss the so-called "semantic conception of theories", then I present my own synthesis of how theories and their empirical confrontation should be construed, and in a final note, I give some very general options on how theories would represent reality.

samedi 6 août 2016

Structural realism or modal empiricism?

Welcome to this new blog dedicated to the philosophy of science. I already have two blogs, but they're in French, so I decided to make a new one in English. Not that I don't like to write in French. It's a lot easier: my style is more fluid and precise than in English. I also like the idea of keeping my home language alive, especially in philosophy, as English is increasingly becoming the only language in town. But having a blog in English will allow me to share my thoughts with a wider audience, or so I hope. (Please excuse my language mistakes and correct me any time in comments, that's how I'll improve!).

One of my purpose here will be to share in an informal way the content of my PhD dissertation, which I'm currently writing. The dissertation mainly talks about epistemological issues in science, with a little metaphysics. To be precise, I defend a position in the debate on scientific realism, which I dubbed "modal empiricism". I think it's an original position (although the term appears with the same intended meaning in a chapter by Giere in "Images of Science: Essays on Realism and Empiricism", 1985). The position can be expressed in more than one way, but here is one: our best scientific theories are correct descriptions of the relations of necessity between our observations and interventions. Here is another one: all that we know is that our theories are empirically adequate, but the empirical content of our theories is modal: it's about possible experiences.

There is a lot to say, but I think that this position has lots of virtues. For a start, let me say a word about how I came to defend it. The readers familiar with structural realism and Newman's objection can skip to the last paragraph of this post.