Natural Properties and Atomicity in Modal Realism

Abstract

The paper pinpoints certain unrecognized difficulties that surface for recombination and duplication in modal realism when we ask whether the following inter-world fixity claims hold true: 1) A property is perfectly natural in a world iff it is perfectly natural in every world where it is instantiated; 2) Something is mereologically atomic in a world iff all of its duplicates in every world are atomic. In connection to 1), the hypothesis of idlers prompts four variants of Lewis’s doctrine of perfectly natural properties, all deemed unsatisfactory for the purposes of duplication and recombination. By means of 2), instead, we show that the principle of recombination does not countenance the atomicity or non-atomicity of duplicates; but it should, because it is genuinely possible that: a) something, which is atomic, is non-atomic; and b) something, which is non-atomic, is atomic. In discussing 1) and 2), the paper substantiates a tension in Lewis’s metaphysics between modal intuitions and the reliance on the natural sciences.

The Necessity of Naturalness

“…Taking this into consideration, we tentatively endorse the claim that a property is natural if and only if it features in the natural laws of some world. 17 Notably, Borghini and Lando (2015) raise an objection to a version of this proposal. Suppose that we have two perfectly natural properties G and F which are instantiated in worlds w 1 and w 2 , and that F is idle in both worlds.…”

“…Hildebrand (2016) discusses a version of this point with regards to universals.6 Natural properties raise a host of epistemological questions-most pressingly, how do we discover which properties are natural? SeeLewis (2009),Dorr and Hawthorne (2013), andBorghini and Lando (2015) for some discussion of this and related issues. Here we set the epistemology of naturalness aside and assume a god's-eye view in distinguishing the perfectly natural properties from less natural ones.…”