HPCK and Modal Representations

It's been a busy month, moving into a new flat and starting an MSc. I'm studying full time again, which in terms of blogging is a mixed blessing - lots of material, but very little time.

It's nice when you can combine two previously isolated ideas, and that's what I'm going to try and do today. One comes from the philosophy of science, Boyd's "homeostatic property cluster" theory of natural kinds, and the other is an idea from the philosophy of mind, that our mental images might not be entirely separate from our sensory perception.

I'll start with modal representations, because they're probably simpler. A mental representation is basically a mental state that stands for some part of the external world (Clark 1997: 463), whatever we take that to mean. Mental representation is a thorny topic, but all I'm interested in here is one aspect of the issue: whether such representations are composed of sensory information (modal) or are purely abstract (amodal). For example, does our representation of a sunny day call to mind the pleasant feeling of the sun on our skin, or do we somehow comprehend it in isolation from any sensation? For the previous century (analytic) philosophers tended to pick the latter option, no doubt influenced by classical logic, but some (relatively) recent experiments have questioned that assumption. It seems that there is a systematic connection between representations and the sensory qualities of what they represent, as demonstrated by experiments such as those conducted by Zwan, Stanfield & Yaxley (2002) and by Glenberg & Kaschak (2002). The implications of these experiments are still being debated, but one interpretation is that our representations (and by extension, our concepts) are composed of bundles of modal (sensory) data, rather than discrete, amodal definitions.

This is where Boyd comes in. His theory is a form of realism about natural kinds, but I think that it shares some interesting similarities with the idea of modal properties. Motivated by the messiness of biological kinds, Boyd characterises a natural kind as sharing a cluster of properties, none of which are necessary or sufficient. These kinds are rooted in the causal structure of the world, and are thus real, but they allow for the flexibility that is necessary when it comes to biological kinds. Given that our access to kinds is mediated by our senses, I think it might make sense to identify the modal bundles that I described above with Boyd's property clusters. Our concept or representation of a cow might consist of the vague appearance of a cow, the smell of cow dung, and the monotonous sound they make - and this will in some sense correspond with (at least some of) the properties in the natural kind cluster "cow". Boyd's point is that there doesn't have to be an exact matching for every instantiation of a natural kind, so everyone's perception of cow's can (and will) be subtly different.

I still haven't quite got to grips with Boyd's theory, and I'm not sure how much he would support this idea, but I think it could allow for an evolutionary justification of how classify natural kinds. This would be similar to Quine's empiricist position (see his 1969), and might not be as realist as Boyd would like.

• Clark, A. 1997. "The Dynamical Challenge." Cognitive Science 21(4): 461-81.
• Glenberg, A. & Kaschak, M. 2002. "Grounding language in action." Psychonomic Bulletin and Review 9: 558-65.
• Quine, W.V.O. 1969."Natural Kinds." In Ontological Relativity and Other Essays. New York and London: Columbia University Press.
• Zwan, R., Stanfield, R. & Yaxley, R. 2002. "Language comprehenders routinely represent the shape of objects?" Psychological Science 13: 168-71.