Full Idea
Natural kinds appear to be of objects or substances, or of events or processes, or of the intrinsic nature of things; hence there should be laws of nature specific to each of these categories.
Gist of Idea
Natural kinds are of objects/substances, or events/processes, or intrinsic natures
Source
Brian Ellis (The Philosophy of Nature: new essentialism [2002], Ch.5)
Book Reference
Ellis,Brian: 'The Philosophy of Nature: new essentialism' [Acumen 2002], p.82
A Reaction
It is nice to see someone actually discussing what sort of natural kinds there are, instead of getting bogged down in how natural kinds terms get their meaning or reference. Ellis recognises that 'intrinsic nature' needs some discussion.