The Metaphysics of Laws: Dispositionalism vs. Primitivism

The Metaphysics of Laws: Dispositionalism vs. Primitivism

Mauro Dorato and Michael Esfeld

The paper compares dispositionalism about laws of nature with primitivism. It argues that while the distinction between these two positions can be drawn in a clear-cut manner in classical mechanics, it is less clear in quantum mechanics, due to quantum non-locality. Nonetheless, the paper points out advantages for dispositionalism in comparison to primitivism also in the area of quantum mechanics, and of contemporary physics in general.

In this paper we will assume that the main dividing line runs between Humeanism on the one hand and primitivism as well as dispositionalism on the other. Humeanism has to accept the whole distribution of the local matters of particular fact as a primitive, since the laws, being the axioms of the description of that distribution that achieve the best balance between simplicity and empirical content, supervene only on that entire distribution. In a nutshell, thus, what the laws of nature are, is fixed only "at the end of the world".

It is not the laws that determine the development of the world, but it is the development of the world, in the sense of its spatiotemporal arrangement, that determines what the laws are (see Beebee and Mele 2002, pp. 201-205). By contrast, primitivism and dispositionalism have only to accept the initial conditions of the world Ð such as an initial configuration of point-particles in a background spacetime Ð as a primitive. The initial conditions, plus the fact that (i) certain laws are instantiated in the world in question (primitivism about laws) or that (ii) the instantiation of certain properties (dispositions) is part and parcel of the initial conditions (dispositionalism), fix the further development of the world. The reason for this divergence is that Humeanism eschews a commitment to objective modality, whereas both primitivism and dispositionalism subscribe to it. According to Humeanism, there is nothing about any proper part of the distribution of the local matters of particular fact in a world that fixes what is physically possible and what is not possible as regards the rest of the distribution of the local matters of particular fact in the world under consideration. The physical modality in question is not Òin reÓ, but belongs to the model or is a purely linguistic feature of nomic statements. According to both primitivism and dispositionalism, by contrast, there is something about a proper part of the distribution of the local matters of particular fact in a world that fixes what is physically possible and what is not possible in the world at issue, because either laws or a set of dispositional properties respectively are instantiated everywhere in the world.