Notes on Quine’s famous paper: Natural Kinds
Quine, Willard Van Orman. 1969. Natural Kinds. in Ontological Relativity and Other Essays: Columbia Univ. Press.
The paper starts with a problem for induction: “What tends to confirm an induction?” He relates Hempel’s puzzle of the non-black non-ravens and Goodman’s puzzle of the grue emeralds to an innate sense we have for similarity and sorting into kinds. First of all, we need to understand projection. The grue problem: this has been difficult for me to get my head around and it seems to have some complex logic problems, not to mention much discussion across the net around its implications and predicates. All emeralds studied before 2013 are green, so induction would suggest that all emeralds are green. Simple enough. However, at time t all emeralds turn blue but we do not know this yet. An emerald that has turned from green to blue is grue. So all emeralds studied after time t in 2013 will be grue and hence blue. The predicate green is projectable, the predicate grue is not, as who is to know that the emeralds are going to change color? Some discussions on this have broadened the context to suggest other precious stones change color in the same fashion creating a precedent and likelihood that emeralds will change color, therefore can you use induction to conclude that all emeralds are grue?
A projectable predicate counts towards the confirmation of all x‘s are z‘s. Quine uses projectability to solve the black raven, non-black non-raven problem. ‘Black’ and ‘raven’ are projectable, though ‘non-black’ and ‘non-raven’ are not. Hence, the raven problem is not an induction problem as induction only runs in the same direction as projectability. However, the proposition ‘all non-black things are non-ravens‘ is still lawlike, as it is logically equivalent to ‘all x are y‘.
“A projectable predicate is one that is true of all and only the things of a kind. What makes Goodman’s example a puzzle, however, is the dubious scientific standing of a general notion of similarity, or of kind.” (p116)
Quine then turns his attention from projectability to the problem of determining a ‘property’ as we need to sort kinds via their common properties. The point of projectability was to first outline how we might have confidence in our inductions about kinds in a temporal setting. He then illustrates how fundamental the notion of similarity or kind is to our thinking, yet how alien it is to logic and set theory. The non-logical roots of similarity and kind are important.
“One part of the problem of induction, the part that asks why there should be regularities in nature at all, can, I think, be dismissed. That there are or have been regularities, for whatever reason, is an established fact of science; and we cannot ask better than that. Why there have been regularities is an obscure question, for it is hard to see what would count as an answer. What does make clear sense is this other part of the problem of induction: why does our innate subjective spacing of qualities accord so well with the functionally relevant groupings in nature as to make our inductions tend to come out right? Why should our subjective spacing of qualities have a special purchase on nature and a lien on the future?” (p126)
Quine turns to Darwin and suggests that people’s innate spacing of qualities is a gene-linked trait, and that successful inductions will have become predominate through natural selection. He asserts that he is not generalising or creating a priori arguments. He wants to demonstrate that the ‘innateness’ he is describing is not an argument against empiricism. Rather than innate ideas (rationalists – continental) he is describing innate capacities (empirical – Darwin). He sees philosophy as continuous with science, with no external vantage point (no foundationalism – Quinean holism). Therefore all scientific findings that are at present plausible can be used a specificity in philosophy as elsewhere.
Important: Kornblith departs from Quine on this point. He asserts that we can survive without our cognitive capacities being accurate; see chpt 1.
He next acknowledges inductions conspicuous failures. He uses the sense-input data we have as humans as an example, primarily color. We are well aware of our sense data limitations, yet in spite of an array of inductive errors made in such a context we have still been successful. This boils down to the human condition whereby our limitations have helped us survive on one hand, i.e. color is helpful at the food gathering level, but on the other are insignificant to such activities as broader theoretical science. So there is a dynamic existence and use of sense data and innate similarity biases. Essentially, it is the achievement of the species to have risen above, using inductive inference, his sensory limitations and sensory space. Induction has allowed a trial and error process of theorizing and therefore has a definite temporal quality/factor that needs to be included in any justification discussion of induction:
“A crude example is the modification of the notion of fish by excluding whales and porpoises. Another taxonomic example is the grouping of kangaroos, opossums, and marsupial mice in a single kind, marsupials, while excluding ordinary mice. By primitive standards the marsupial mouse is more similar to the ordinary mouse than to the kangaroo; by theoretical standards the reverse is true.” (p128)