Natural powers and laws of nature

Max Kistler

Is has been argued recently that, within the metaphysics of natural properties as powers, laws of nature need not be postulated over and above the natural properties themselves (Mumford 2004; Bird 2007). However, the metaphysics of sciences requires both laws and powerful properties.

Natural properties can be construed in a “thin” or a “thick” way. If one attributes an object a property in the thin sense, this attribution does not conceptually determine which other properties the object possesses. The thin construal is underlying the scientific strategy for understanding nature piecemeal. Properties are conceived of independently of each other. In a separate step, one enquires to which other properties they are related; those determination relations between properties are laws. The dispositions a property gives its bearer are determined by the laws containing this property.

For example, electrical conductivity s gives a copper wire

1) the disposition to react to a field E with a current of density J (by Ohm’s law),

2) the disposition to give rise to a magnetic field B (by Ampere’s law).

This relation to the magnetic field B gives the copper wire still more dispositions, by virtue of B’s lawful relations to other properties.

In the thin conception, all these properties are taken to be distinct from each other.  This is compatible with taking laws to be metaphysically necessary.

According to the thick conception, a property contains all the dependency relations to other properties. The dependency relationships (which appear as laws in the thin conception of properties) between properties areparts of the properties they relate. Properties are “clusters of powers” (Mumford 2004, p. 302) or “clusters of relations with other properties” (p. 17).

I will give several reasons to resist the thick conception of properties: It makes monadic properties relational. It makes simple properties “holistic”, in the sense that each property contains many other properties as parts. It makes invisible relations between powers belonging to different properties. It blurs the distinction between logical and natural necessity.

Metaphysics should postulate all entities (and only those) whose existence is needed to make sense of science. Science explains phenomena by cutting reality conceptually in properties attributed to space-time points, and then exploring how these properties are related to each other. These links of dependency between properties are laws. Metaphysics should follow science in postulating laws alongside properties.


Mumford, Stephen (2004), Laws In Nature, London, Routledge.
Bird, Alexander (2007), Nature’s Metaphysics. Laws and Properties, Clarendon Press.