_______________________________________________________________________________
Introduction
The Homeostatic Property Cluster (HPC) view of natural kinds is an attempt to reconcile the heterogeneity found within kinds (particularly biological kinds like species) with the fact that kinds are nevertheless non-arbitrary categories that are useful in scientific theories (Brigandt 4). While the HPC view is now generally regarded as the best approach to natural kinds, it is not without its critics. One such critic is Carl Craver, who argues in “Mechanisms and Natural Kinds” that the HPC view incorporates conventionalist elements into its theory. If so, then the HPC view is not the realist theory of natural kinds it claims to be and thus cannot “serve as an objective arbiter in scientific disputes about what the kinds of the special sciences should be” (Craver 575). In this paper I will briefly explain what Craver takes to be the HPC view and then explain his criticisms. Following, I will defend and critique the HPC view. I find that Craver has mischaracterized the HPC view, but that his mischaracterization rests on plausible assumptions that the HPC view denies. Thus, I believe that many of Craver’s underlying concerns are legitimate. I conclude by explaining how an HPC theorist might accommodate Craver’s assumptions while still resisting his conclusion, thereby finding that a suitably revised HPC view is a realist approach to natural kinds.
The HPC View
According to Craver, the HPC view claims that natural kinds track mechanisms that sustain property clusters in a stable way. Craver defines mechanisms as “entities and activities organized together such that they do something” (Craver 582). When it comes to homeostatic mechanisms, the entities and activities organized in a certain way have the power to generate and sustain property clusters that we pick out as making up a kind. Thus, it is because of the operation of these homeostatic mechanisms that these property clusters exist. As such, one can use homeostatic mechanisms to individuate kinds (and so these can be thought of as essences of the kinds); the natural kind is delineated by the homeostatic mechanism(s) that sustain(s) it and so the homeostatic mechanisms “determine the boundary and integrity of the kind” (Brigandt 9).[1] Mechanisms can operate on both relational (external) and intrinsic (internal) properties and so whether an individual is part of a natural kind partly depends on features external to that individual (Boyd 153, Brigandt 5). [2]
The HPC view, as Craver understands it, is supposed to offer an objective view of natural kinds. The homeostatic mechanisms “constitute the causal structure of the world,” and so “nature’s joints are located at the boundaries of mechanisms” (Craver 575). Natural kinds are “real divisions in the structure of the world,” and these divisions track the divisions of homeostatic mechanisms (Craver 577). Thus, kinds are given to us by nature; they are discovered, not created. However, because kinds track the causal structure of the world by following divisions among mechanisms, they are useful and predictive in scientific theories that use the property clusters to make generalizations and predictions.
The HPC view sits between essentialism on one side and conventionalism on the other. Traditional essentialists claim that “natural kinds are defined by necessary and sufficient conditions, that is, the set of properties shared by all and only members of the kind” (Craver 577). The HPC view differs from essentialism in that no set of properties is necessary and sufficient for kind membership. A member of a kind merely needs to have enough properties that are part of a property cluster that defines a kind. Furthermore, HPC theorists take natural kinds to have fuzzy boundaries, whereas an essentialist will have clear boundaries regarding which entities are members of a kind and which members are not. The lack of clear boundaries allows HPC theorists to count biological kinds as natural kinds in spite of the great variability amongst individuals that seems to preclude necessary and sufficient conditions for kind membership.
On the other side, conventionalists about natural kinds claim that “the difference between natural kinds and merely conventional property clusters lies not in the phenomena themselves but in the psychological or social factors that determine how human beings find it useful to chunk the world for a given purpose” (Craver 576). That is, “natural” kinds are merely those property clusters that humans find most interesting and important for their purposes but which are not grouped by anything purely natural or objective with regards to the structure of the world. Thus, “some kinds are more useful or interesting to us than others, but there is no (or need be no) further fact about the world that explains why this is so. The natural kinds are merely the useful ones” (Craver 577). In contrast, the HPC view wishes to preserve the naturalness and objectivity of natural kinds, locating this naturalness in the features of entities themselves and not merely in the usefulness that such groupings provide for humans.
There is one final aspect of the HPC view as traditionally formulated by Boyd that needs to be discussed: the Accommodation Thesis. Craver understands the Accommodation Thesis as claiming that “any refinement of the definition of the kind either introduces causally and inductively irrelevant distinctions or glosses over causally and inductively relevant similarities” (Craver 578). What does this mean? Craver gives two possible interpretations. The first is a strong reading that claims that “the correct taxonomy of natural kinds must be immune to revision in light of future discoveries about the mechanistic structure of the world” (Craver 579). This would suggest that the correct taxonomy will never need to be adjusted in light of future discoveries and so it does in fact categorize the world correctly. The second is a weaker reading that our taxonomy of kinds should “pick out sets of things that are similar enough for our explanatory or instrumental projects” (Craver 579). On this reading, what matters is that our taxonomy serves the purposes of scientists and so a “correct” taxonomy will continue to do so in the future. Which of these two readings is correct will be addressed in responding to Craver’s fifth objection.
Continued on page 2
No comments:
Post a Comment