Philosophy of Biology and Cognitive Sciences

In a series of articles, Martha Nussbaum has developed a theory of animal rights grounded in her version of the “capability approach.” According to this theory, particular organisms (and only particular organisms) have rights to its specific form of dignity, which means rights to particular capabilities corresponding to its “characteristic activities” (see e.g. Nussbaum 2007, 365) . Its characteristic activities, in turn, are given by its biological species. Nussbaum argues that the capability approach’s attention to these characteristic activities or species-typical functions better recognizes the diversity of forms animal well-being takes compared to utilitarianism or other theories of animal rights. Her view’s individualist view of value also rejects sum-ranking and aggregation of well-being across organisms.

 

I show that the Aristotelian elements of Nussbaum’s view of animal well-being commit her to an essentialist view of species. On Nussbaum’s view, an individual’s species grounds its well-being or makes it the case that an individual has a well-being, and its species also provides a criterion for its well-being. According to essentialism about species, a species’ essence occurs in all and only the members of a kind, it plays a central role in explaining the properties typically associated with the members of a kind, and an essence is an intrinsic feature of the organism (Ereshefsky 2007) . For Nussbaum, an organism’s species explains or makes it the case that it has a well-being. In addition, it also matters for Nussbaum’s view that an organism’s essence as a criterion for well-being manifests in observable and typical behavior. This condition makes an organism’s well-being is epistemically accessible to observers. Finally, because of her reliance on an organism’s species as the criterion for its well-being, and as well as her moral individualism, Nussbaum must assume that typical species behavior is generally reliable evidence for a particular organism’s well-being.

Essentialism about species, then, has a metaphysical and epistemic role in Nussbaum’s theory: an organism’s essence as species-token both grounds and provides the criterion for its well-being. Furthermore, her moral individualism requires that species-typical behavior provide reliable evidence for a particular organism’s well-being. I argue next that Nussbaum’s metaphysical and epistemic claims about species are in tension with widely accepted positions in evolutionary biology and the philosophy of biology. First, work on the ontology of species in biology over the last fifty years has steadily undermined the essentialist view, beginning with the work of Michael Ghiselin (1966) and David Hull (1965) . Second, evolutionary biologists have identified a number of mechanisms for divergence between species-typical behavior and the well-being of individual organisms. Multiple levels of selection, especially group selection, as well as mechanisms such as costly signaling and the “handicap principle,” suggest that species behavior may be not be a reliable criterion for the well-being of particular organisms. Group selection, for example, means that the reproductive fitness of a population may improve at the expense of the fitness of some organisms in the population.

 

I argue that these two sources of tension, then, raise two separate concerns for the relationship in Nussbaum’s theory between an organism’s welfare and the “characteristic activities” of its biological species. First, the conceptual connection it asserts between an organism’s welfare andits species identity is relies on a questionable metaphysical assumption. Second, and separate from the question of how the ontology of species should be understood, the “characteristic activities” of its species do not provide reliable evidence for an organism’s well-being. In conclusion, I suggest weakening the moral and conceptual role of species-typical behavior in Nussbaum’s theory of animal rights.