Full Idea
Natural kinds are said to stand out from other classifications because they support legitimate inductive inferences ...as when we observe that past samples of copper conduct electricity and infer that the next sample will too.
Gist of Idea
Natural kinds support inductive inferences, from previous samples to the next one
Source
Kathrin Koslicki (The Structure of Objects [2008], 8.3.1)
Book Reference
Koslicki,Kathrin: 'The Structure of Objects' [OUP 2008], p.204
A Reaction
A slightly more precise version of the Upanishad definition of natural kinds which I favour (Idea 8153). If you can't predict the next one from the previous one, it isn't a natural kind. You can't quite predict the next tiger from the previous one.
Related Idea
Idea 8153 By knowing one piece of clay or gold, you know all of clay or gold [Anon (Upan)]