Dylan goes on location to St. John's College, Annapolis to talk with Stewart Umphrey about his book Natural Kinds and Genesis: The Classification of Material Entities (2016), with Mark and Wes lobbing in questions remotely.
Are general terms like "water" or "dog" or even "chair" just things that we made up to order the world we experience? Aristotle thought that some universals (not "chair," but the other two) constitute natural kinds, with an internal structure that explains their behavior. This kind of talk was replaced with the scientific revolution with talk of laws instead of kinds, but Stewart wants to revive this notion, as well as the activity of "natural philosophy," which was what folks like Descartes and Newton considered themselves to be doing, but which subsequently stopped being a thing when the natural sciences broke off from philosophy.
We all read chs. 1–5 and the epilogue, and each chapter focuses on a different topic: Ch. 1 covers the preconditions of natural philosophy, which include a rejection (as an assumption for inquiry, not as a final conclusion) of any kind of idealism and acceptance that there really is an external world apart from our cognition. Ch. 2 then covers universals: Stewart thinks it reasonable to hypothesize that these are real contra nominalism that says we just make up all of the concepts we use to organize things. Ch. 3 gets to continuants, which are things that we see as existing over time, even though their location, or many of their properties may change; his example is a particular squirrel, whereas "water" as a mass wouldn't qualify (though a particular water molecule would). Again, after considering the available positions pro and con re. the existence of his subject, he concludes that it's a reasonable bet that there are legitimate continuants. Finally, in ch. 4 he gets to natural kinds, which he argues constitute the essence of a continuant type, e.g., what makes a squirrel or water molecule what it is. His view entails that each continuant can only be one natural kind, so while "squirrel" may end up to be a natural kind, then "animal" or other nested categorizations would not be; those would be just concepts of convenience, not ultimate parts of our ontology. Dylan also read chs. 6 and 7, which bring in concrete examples from biology and physics, so these will be discussed in part 2.
The purpose of caring about ontology in this way is to argue against the long-time scientific goal of reducing all of psychology to biology, all of biology to chemistry, and then to physics. Natural kinds would be irreducible elements in the ontology, not just things that came up in the course of the contingent (i.e., could have gone differently) history of science (contra Rorty). This is not to say that we might not be wrong about what we think the natural kinds are, but if there are some in the way that Stewart describes, then we can talk about real emergence in science: how biological organisms exhibit properties that can't be predicted by looking at things on a lower (e.g., chemical) level.
This is one of our more difficult episodes, and it would certainly behoove you to listen to some of our previous discussions in metaphysics before tackling this one. For instance, ep. 130 on Aristotle's De Anima, ep. 126 on Saul Kripke, ep. 6 on Leibniz's monads, and ep 68. where we talked to David Chalmers about metaphysical reductionism.
Here's an article Wes wrote about the relationship between science and philosophy where he mentions Stewart.
Update: Order the book at www.rowman.com and use the code LEX30AUTH17, you'll get 30% off your order.