On a naturalist theory of health: a critique.

This paper examines the most influential naturalist theory of health, Christopher Boorse's 'biostatistical theory' (BST). I argue that the BST is an unsuitable candidate for the rôle that Boorse has cast it to play, namely, to underpin medicine with a theoretical, value-free science of health and disease. Following the literature, I distinguish between "real" changes and "mere Cambridge changes" in terms of the difference between an individual's intrinsic and relational properties and argue that the framework of the BST essentially implies a Cambridge-change criterion. The examination reveals that this implicit criterion commits the BST to the troubling view that an individual could go from being diseased to healthy, or vice versa, without any physiological change in that individual. Two problems follow: (1) the current framework of the BST is ill-equipped to formally embrace Cambridge changes and (2) it is theoretically dubious. The arguments advanced here are not limited to the BST; I suggest they extend to any naturalist claim to underpin medical practice with a value-free theory of health and disease defined in terms of an evolutionary view of biological fitness.