In lieu of an abstract, here is a brief excerpt of the content:Philosophy, Psychiatry, & Psychology 9.3 (2002) 219-227 [Access article in PDF] The Practical Kinds Model as a Pragmatist Theory of Classification Peter Zachar Pragmatist theories of scientific classification are intended to be pluralistic models that recognize different ways of cutting up the world as valuable, but do not require us to adopt whatever-goes relativism or metaphysical antirealism. How ironic that my application of pragmatism to psychopathology has been charged (...) with not being sufficiently pluralistic because it tries to fit all psychiatric disorders into the Procrustean bed of practical kinds. The Practical Kinds Model in General As a point of clarification, the practical kinds model is not a description of a type of category combined with an argument that all psychiatric disorders should be seen as belonging to that type. If it were that kind of model, I would fully agree with Haslam that practical kinds, fuzzy kinds, and discrete kinds are all potential types of psychiatric disorders. Like Nick Haslam, I believe that there are many different things in the DSM-IV and the ICD-10, and they cannot neatly be classified as the same type of thing.Rather than identifying a type of category, the practical kinds model is a general theory of scientific classification. It is a nonessentialistic theory. Essentialism is the view that things have real essences. In the Aristotelian version of essentialism, an essence is an internal structure, and it is the internal structure that makes anything be the kind of thing it really is. In this classical category model, category members either have the essence or they do not, and everything that has the appropriate essence is a member of that category. The world is supposed to therefore have a well-defined structure, and the job of the scientist is to discover that structure. Ian Hacking (1999) has termed this view of categorization inherent structurism.The practical kinds model does not deny that things have internal structures; it only denies that internal structure by itself determines category membership. Internal structure is an important consideration in identifying categories, but external criteria can always play a role. External or relational criteria play more important roles in some cases than they do in others, but they cannot be eliminated once and for all. Essentialistic theories, which favor an almost exclusive focus on inherent structures, have the advantage of being more parsimonious, but they do so by ignoring real complexity.The best way to illustrate this point is to examine a category whose identification is heavily weighted in terms of internal criteria, or an inherent structure, such as a chemical element. [End Page 219] For example, hydrogen is defined as the element that has an atomic number of 1. This means that it has one proton in its nucleus and normally one electron orbiting its nucleus. The atomic number reflects an internal property, and anything that has an atomic number of 1 is hydrogen. The same is true for the other elements. Anything that has an atomic number of 79 is gold; anything that has an atomic number of 19 is potassium, and so on. Also part of the essentialistic view is the notion that all the important properties of an element are systematically (or lawfully) related to its internal structure.It would be foolish to deny the practical utility of the atomic theory of chemistry. But even in this strongest of cases, external criteria can potentially play a role in how we decide to carve up the world and what we identify as the relevant categories. The point can be clearly illustrated with a Gedanken experiment based on the ideas of Donnellan (1983). Assume that we were to make contact with extraterrestrial life, and the result of that contact was our initiation into a larger galactic community like those portrayed on Star Trek or Babylon 5. Fortunately for us, it turns out that all planets in the community use a gold-based currency, just like we do on Earth. What we call gold, however, is too common to be the galactic basis of a currency, but a particular isotope... (shrink)

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Essentialism is widely regarded as a mistaken view of biological kinds, such as species. After recounting why (sections 2-3), we provide a brief survey of the chief responses to the “death of essentialism” in the philosophy of biology (section 4). We then develop one of these responses, the claim that biological kinds are homeostatic property clusters (sections 5-6) illustrating this view with several novel examples (section 7). Although this view was first expressed 20 years ago, and has received recent discussion (...) and critique, it remains underdeveloped and is often misrepresented by its critics (section 8). (shrink)

The pivotal problem of comorbidity research lies in the psychometric foundation it rests on, that is, latent variable theory, in which a mental disorder is viewed as a latent variable that causes a constellation of symptoms. From this perspective, comorbidity is a (bi)directional relationship between multiple latent variables. We argue that such a latent variable perspective encounters serious problems in the study of comorbidity, and offer a radically different conceptualization in terms of a network approach, where comorbidity is hypothesized to (...) arise from direct relations between symptoms of multiple disorders. We propose a method to visualize comorbidity networks and, based on an empirical network for major depression and generalized anxiety, we argue that this approach generates realistic hypotheses about pathways to comorbidity, overlapping symptoms, and diagnostic boundaries, that are not naturally accommodated by latent variable models: Some pathways to comorbidity through the symptom space are more likely than others; those pathways generally have the same direction (i.e., from symptoms of one disorder to symptoms of the other); overlapping symptoms play an important role in comorbidity; and boundaries between diagnostic categories are necessarily fuzzy. (shrink)

The thesis of this article is that an attitude akin to pragmatism is internal to the scientific enterprise itself, and as a result many scientists will make the same types of non-essentialistic interpretations of their subject matter that are made by pragmatists. This is demonstrably true with respect to those scientists who study the biological basis of emotion such as Panksepp, LeDoux, and Damasio. Even though these scientists are also influenced by what cognitive psychologists call the essentialist bias, their research (...) programs are coherent with Peter Zachar?s rejection of natural kinds in favor of practical kinds. When the confrontation with complexity leads a scientist to offer non-essentialist interpretations, two popular options are to go eliminativist or go nominalist. Pragmatists prefer the nominalistic option, and we provide reasons for suggesting that scientists should as well. (shrink)

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