Powers, dispositions and laws of nature

Metaphysics should follow science in postulating laws alongside properties. I defend this claim against the claim that natural properties conceived as powers make laws of nature redundant. Natural properties can be construed in a “thin” or a “thick” way. If one attributes a property in the thin sense to an object, this attribution does not conceptually determine which other properties the object possesses. The thin construal is underlying the scientific strategy for understanding nature piecemeal. Science explains phenomena by cutting reality conceptually in properties attributed to space-time points, where these properties are conceived of independently of each other, to explore then, in a separate step, how the properties are related to each other; those determination relations between properties are laws. This is compatible with the thesis that laws are metaphysically necessary. According to the thick conception, a property contains all its dependency relations to other properties. The dependency relationships between properties (which appear as laws in the thin conception) are parts of the properties they relate. There are several reasons to resist the thick conception of properties. It makes simple properties “holistic”, in the sense that each property contains many other properties as parts. It cannot account for the fact that properties constrain each other’s identity; it can neither explain why natural properties are linked to a unique set of dispositions, nor why and how this set is structured nor why the truth-maker of many disposition attributions is relational although the disposition is grounded on a monadic property.