Vol.:(0123456789) Biology & Philosophy (2020) 35:7 https://doi.org/10.1007/s10539-019-9709-8 1 3 Pathogen versus microbiome causation in the holobiont Aja Watkins 1  · Federica Bocchi 1 Received: 16 July 2019 / Accepted: 3 October 2019 © Springer Nature B.V. 2019 Abstract In their paper “How Causal are Microbiomes? A Comparison with the Helicobac- ter pylori Explanation of Ulcers,” Lynch, Parke, and O’Malley successfully argue that certain causal attributions made to the microbiome have not satisfed Koch’s postulates nor the interventionist framework. However, their argument involves an implicit assumption that cases such as H. pylori are sufciently similar to cases involving the microbiome, such that causal attributions to both should be evaluated according to the same causal framework. Our commentary targets this assumption. First, we introduce the historical circumstances that led to the formulation of Koch’s postulates in order to diferentiate the case of the microbiome from that of infec- tious bacteria. Then, we introduce the concept of the holobiont, the idea that hosts and their symbionts should be conceptualized as a metaphysical and biological unit. Finally, using the holobiont concept, we argue that Koch’s postulates and the inter- ventionist framework are ill-equipped to handle the microbiome. We conclude by suggesting that a revision of what counts as microbiological causality within the holobiont is justifed. Keywords Microbiology · Microbiome · Holobiont · Biological causation Introduction Lynch et al. (2019) successfully argue that certain causal attributions made to the microbiome have not satisfed Koch’s postulates nor the interventionist framework. However, their argument involves an implicit assumption that cases such as H. pylori are sufciently similar to cases involving the microbiome, such that causal attribu- tions to both should be evaluated according to the same causal framework. This comment refers to the article available at https://doi.org/10.1007/s10539-019-9702-2. * Aja Watkins ajawatki@bu.edu 1 Philosophy Department, Boston University, 745 Commonwealth Ave, Boston, MA 02215, USA