Archives For Science

Quine – Natural Kinds

October 25, 2012 — 4 Comments

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)


What is IBE?

Simply, IBE is using logical inference to create a hypothesis that accounts for reliable data, or seeks to explain relevant evidence i.e. the lawn/street etc is wet in the morning, therefore IBE would lead us to hypothesize that it rained last night. IBE also seeks to make the most economic explanation, hence the use of the word ‘best’ in the title.

Kornblith employs IBE to argue from success of science to existence of natural kinds. This raises the question of induction (the success of science can be accounted for by natural kinds, using IBE as the method to make such a hypothesis).

IBE: a form of inference in it’s own right, rather than a form of induction or deduction.

Problems with IBE:

Putting Inference to the Best Explanation in its Place – T Day & H Kincaid

“Within epistemology, IBE is used in at least two ways: as a fundamental rule of belief revision or as a strategy for showing that a favored account of justification has the needed ties to truth.” (p272)

Harman claims that all inductive inference is IBE. IBE as the basic rule of justification is useful for foundationalists. i.e. Moser, for whom foundations are subjective non-conceptual contents, non-propositional experiences that can justify propositions when the propositions are the best explanation for non-conceptual contents. IBE also appeals to truth; just think of Kornblith’s argument for the success of science, or propositions that hold up in comparison with the natural over time.

Van Fraassen sees IBE as worthless. He asserts that it makes us ‘incoherent’:

“… any IBE will work only given some hypotheses to choose from. However, unless we that the relevant contenders probably contain the truth, then inferring to the best explanation does not up the odds that we are picking the true one. Moreover, our current science is just one of many possible accounts of the world, most of which we cannot even state and most of which of course must be false. Thus our own current views must be taken as a random member of the total possible explanations, and thus as probably not true. Thus even if our current theories were the best explanation, that would be no ground for taking them to be true.” (p274)

There is no detailed explanation of IBE by its defenders or detractors. This chapter points out two basic approaches to explanation: unification and causation. If we understand IBE as unification, then 1) IBE collapses into nothing more than coherence with the totality of belief and evidence, thus making IBE redundant and uninformative; or 2) IBE is defeasible, limited argument strategy. If explanation is the citing of causes, then likewise IBE is a defeasible, limited argument strategy.

Day and Kincaid suggest a different form of inference, a kind of precursor to IBE: “On the causal interpretation, IBE traded on our background knowledge about causal processes to warrant an inference to one hypothesis over another. This suggests that IBE does not name a fundamental pattern of inference but that it is instead an instance of another, more general inference strategy. That strategy infers to warranted beliefs from background information and data. When those background beliefs essentially involve claims about explanation and those claims ground inferences from the data to new beliefs, this general inference strategy becomes IBE.” (p282)

“In short, appeals to the best explanation are really implicit appeals to substantive empirical assumptions, not to some privileged form of inference. It is the substantive assumptions that do the real work.” (p282)


IBE is useful, but must be evaluated within a context. In general, context of an argument is everything that goes into determining the adequacy of the inference (except for syntax and semantics); background knowledge, internal vs. external evidence, and purposes. Purpose refers to whether the conclusion is intended to fit into an overall doxastic system. Imagine taking an argument to a fellow specialist, who shares a set of assumptions and background knowledge, vs. to a skeptic.

Internal/external: the most internal standpoint allows only the facts that are to be explained as evidence (in the case of the wet lawn and street, only the wetness is to be used as evidence), whereas the most external standpoint is to ask skeptical questions and find evidence that responds to them (the sense data of the observer is incorrect; Descartes demon).

With contextual factors in mind, it can be seen that depending on the availability of background knowledge, or the presence of a common tradition, IBE the force and success of a given IBE can vary in different contexts.

Is Kornblith using IBE in a contextual way?

Scientific realism suggests we have good evidence that current science is in large part approximately true. IBE is used to draw this conclusion. Anti-realists deny this, and argue that IBE begs the question and that realism is not the best explanation for scientific success.

On anti-realists: “In fact, they need a well-confirmed theory of science. Such a theory would have to explain the rise and fall of scientific theories, the practice of science, and so forth, without invoking realist assumptions. That theory would also have to meet reasonable criteria for good science […] needless to say, anti-realists have no such theory.” (p292)

On realists: “To build successfully an IBE argument for realism, they need (1) to show that anti-realist explanations of science are empirically inadequate and (2) to give a clear account of when scientific success argues for realism. They must achieve the first task to show that realism is the best explanation […] Realists need to take on to take on the second task because we have good evidence that false theories sometimes have been predictively successful.” (p292)

It needs to noted and remembered that this discussion itself must be broken into its own specific contexts. Any theory or argument must be (or will likely be) piecemeal. Science is enormous in its scope and its breadth of claims. A ‘unified’ argument for either realism or anti-realism would be powerful, but unlikely. Any combination of both realist and anti-realist outcomes is possible.

The concept of a ‘real kind’, being a collection of unobservable properties, united in nature, jointly responsible for observable properties by which we can classify objects into kinds, is the causal structure in the world required for inductive knowledge to be possible. It is a foundation for inductive inference. Hence the importance of determining the arguments for conventionalism and realism.

Homeostatic Property Clusters:

A concept suggested by Richard Boyd: “Scientific Realism and Naturalistic Epistemology” (1981) & “Realism, Anti-Foundationalism and the Enthusiasm for Natural Kinds” (1991)

“Organisms are so structured as to maintain themselves in certain states.” (Kornblith, p35)

So homeostasis means a cluster of properties, perhaps cells, or biological systems, which work together so as to maintain themselves even the face of changes in the environment. A self maintenance program. These self-maintenance ‘parts’ are unobservables. They give rise to the salient observable properties which draw attention. For Locke, this would be the arrangement of ‘insensible’ parts.

“A natural kind is a cluster of properties which, when realized together in the same substance, work to maintain and reinforce each other, even in the face of changes in the environment.” (Kornblith, p35)

A key point to understand is that not just any arrangement of ‘parts’ is possible. By understanding the details of arrangement of insensible parts (i.e. chemistry) we understand why some arrangements are stable and others not. For instance, H2O is a possible molecule, but HO2 is not. The clustering of observable properties is a direct result of configurations which are possible at the unobservable level. This is the path to explaining what it is about the world that makes it knowable.

“Because there are natural kinds, and thus clusters of properties which reside in homeostatic relationships, we may reliably infer the presence of some of these properties from the presence of others. In short, natural kinds make inductive inference possible…” (Kornblith, p36)

A problem arises:

Remember that in nature we have real kinds, and nominal kinds. Real kinds correspond to homeostatic clusters of unobservables, and nominal kinds are the abstract Idea to which the real kind/essence is attached. However, invoking philosophy of science and turning to unobservables, the question arises whether they are real properties in nature or merely nominal. Therefore we need an account for which unobservable, homeostatic clusters are real, and not nominal. Therefore the argument is postponed by homeostatic clusters, and not concluded.

Kornblith does not worry about such objections:

“Were the postulation of such underlying properties and relationships unrelated to the predictive, explanatory and technological successes of science, there would indeed be reason to think that appealing to such unobservables is nothing more than a sham. But in light of the intimate relationship between the postulation of unobservable structure and the various successes of science, one can no longer reasonably doubt the real existence of such structures.” (Kornblith, p41)


Kornblith suggests that the success of science is the direct result of the postulation of unobservable structure that underlies appearances (essence).

The normative account: is it possible for anything naturalistic in character to have normative value?

Locke’s real and nominal essences are used to discuss natural kinds. Locke’s view on natural kinds shoots in three seperate directions: conventionalist (classification convenient and not accurate) , realist ‘light’ (Locke’s official position; that there are real kinds, though real essences unknowable), and realist (kinds are known with difficulty).

Realism: there are individual things in nature. There are also real kinds of things. They exist, and hence we can discover them. We do not construct them or imagine them. They are real divisions found in nature. Kornblith points out that create categories, which can be accurate/inaccurate or useful/not-useful, but there are real divisions. Such as mammals, further divided into cats and dogs, and into ever smaller categories. Conventionalism suggests that individual things in the world are real, but kinds are not. Categories are a human construct. The classification system is all important.

Notes from the Stanford Encyclopedia

Locke’s philosophy of epistemology is the foundation of his philosophy of science. Being a philosopher of the enlightenment his epistemology is metaphysical, though he took large strides to create a philosophical grounding for the experimental science of the day.

And if he is a devotee of the new science, he often appears an uncertain one, recognizing profound difficulties in it. In consequence, Locke’s work is characterized by tensions and nuances…

On the one hand Locke retains an ideal that all knowledge is demonstrative and certain. A view shared with the Aristotelian’s and Cartesian’s. On the other hand, impressed with empirical methods, he defines a distinct kind of knowledge, one inferior to genuine scientific knowledge but appropriate to human sensory capacities.Locke inherited the philosophical conception of scientia which has roots in Aristotle. Scientia proposes that scientific knowledge is certain knowledge of necessary truths, which can in principle be expressed in syllogistic form, the conclusion following from self-evident premises (deductive). Locke develops the concept of scientia by distinguishing 3 separate kinds of knowledge: intuitive, demonstrative, sensitive.

Intuitive knowledge is the most certain because the truth is grasped immediately. There are no intermediate steps, and doubt is impossible because the mind can no more avoid recognizing the truth than the open, functioning eye could avoid seeing light when turned toward the sun (E See IV.ii.1, p. 531). Demonstrative knowledge, though also qualifying as certain, is less so because it involves intermediate steps. We cannot grasp immediately that the three angles of any triangle are equal to two right triangles, and must instead construct the steps of a proof.

Locke’s objects of scientia: real essences and the necessary conditions that flow from them (causality?). Locke then distinguishes between real essences and nominal essences. The real essence is that which makes the thing what it is, and the nominal essence consists in the set of observable qualities we use to classify a thing (may change over time).

We have scientific knowledge of something when we know its real essence and, since its qualities flow from that real essence, when we know the necessary connections between the essence and its other qualities. Geometry serves as an exemplar, as it did for so many of Locke’s predecessors. In knowing what a triangle is, we cannot conceive things being otherwise than that the sum of its three angles equal the sum of two right angles.

Real essences are impossible for the human being to know, due to the constraints of sense data. Therefore the epistemological question of knowledge needs to be addressed. Locke rejects skepticism. Instead he lowers the bar for what defines knowledge, invoking another kind of knowledge, one which is not certain; sensitive knowledge. This is knowledge of effects that have come to our senses, without us determining or developing an understanding of their cause. Sensitive knowledge does not get to understand real essences, instead it knows only those perceived properties from which we construct nominal essences. Experience.

Has contemporary science enabled us to go beyond sensitive knowledge—have discoveries about compounds, elements, and subatomic particles provided us with knowledge of real essences? Much of the force of this question derives, to paraphrase Nicholas Jolley, from the fact that many of those discoveries about matter’s structure were not conceived empirically, but only confirmed empirically; they were initially conceived as possibilities by employing the hypothetico-deductive model, and the predictions deduced from the models were then compared to empirical data (Jolley 2002, p. 69). Yet as Jolley also points out, these commentators may have missed the full import of Locke’s geometric model; in a passage quoted earlier, Locke tells us explicitly that if we knew the real essence of gold, we could deduce its qualities even if gold did not exist.

Questions to keep in mind on reviewing this book:

What is the problem Kornblith addresses in this book?

How does he characterize the philosophical problem he seeks to solve?

Does Kornblith seeks to address Hume’s problem of induction?

Does he explicitly (or implicitly) suggest that he seeks to justify the use of induction in response to the Humean skeptic?

Karl Popper rethought the idea of foundationalism being a concrete set of assumptions or beliefs upon which knowledge is built. He related his view metaphorically to a swamp in which pillars or structures are sunk to create foundations. THe swamp implies that the empirical foundation of objective science is nothing absolute. Science and its structure and network of theories are a towering edifice that rises out of a swamp of uncertainty and possibility. The foundations are piers going down into the swamp from above. They do not reach a natural base, rather, they stretch down to the necessary degree to support the edifice of theory above.

Notes from Karl Popper: The Formative Years 1902 – 1945