Do relations require underlying intrinsic properties? A physical argument for a metaphysics of relations

TLDR: In this article, the authors define the notion of intrinsic properties as "all and only those qualitative properties that a thing has irrespective of whether or not there are other contingent things; all other qualitative properties are extrinsic or relational".

Abstract: 1. Relations vs. intrinsic properties According to the mainstream of metaphysical thought, the world consists of independent individual things that are embedded in a spatio-temporal framework. These things are individuals, because (a) they have a spatio-temporal location, (b) they are a subject of the predication of properties each and (c) there are some qualitative properties by means of which each of these things is distinguished from all the other ones (at least the spatial-temporal location is such a property). Qualitative properties are all and only those properties whose instantiation does not depend on the existence of any particular individual; properties such as being that individual are hence excluded. These things are independent, because their basic properties are intrinsic ones. Intrinsic are all and only those qualitative properties that a thing has irrespective of whether or not there are other contingent things; all other qualitative properties are extrinsic or relational. That is to say: Having or lacking an intrinsic property is independent of accompaniment or loneliness (see Langton and Lewis (1998) and for a refinement Lewis (2001)). The basic intrinsic properties, as well as the basic relational ones, are not disjunctive; that is to say, properties such as “being round or square” are excluded. This metaphysics can be traced back to Aristotle at least. Aristotle assumes that there is a plurality of individual things (substances) that are characterized by intrinsic properties (forms) each.1 A prominent contemporary formulation is David Lewis’ thesis of Humean supervenience. Lewis writes: ... all there is to the world is a vast mosaic of local matters of particular fact, just one little thing and then another. ... We have geometry: a system of external relations of spatio-temporal distance between points. Maybe points of [6] spacetime itself, maybe point-sized bits of matter or aether or fields, maybe both. And at those points we have local qualities: perfectly natural intrinsic properties which need nothing bigger than a point at which to be instantiated. For short: we have an arrangement of qualities. And that is all. There is no difference without difference in the arrangement of qualities. All else supervenes on that. (1986, pp. IX-X) Thus, there are only local qualities in the sense of intrinsic properties instantiated by spacetime points or point-sized particles at space-time points. Space-time points can qualify as individual things in the above-mentioned sense. Whether everything supervenes on that distribution of basic intrinsic properties is not relevant to the present context. What is