← Pantheon · koch

Koch formalized what Pasteur practiced. Koch's postulates — the agent must be present in every case, isolable in pure culture, capable of reproducing the disease on inoculation, and re-isolable from the new host — give a Kochian argument its skeletal structure. A Kochian argument is a checklist for causal attribution in infectious disease. He demonstrated the tuberculosis bacillus and the cholera vibrio under this framework. Methodologically he privileges pure culture, microscopy with stain protocols, and the inoculation experiment in a susceptible host. A Koch-claimant in a debate will press: which postulate is satisfied, which is not, and is the failure due to the agent or to the method? His characteristic move is the rigorous stepwise satisfaction of each postulate. Weakness: the postulates fail for asymptomatic carriers, viruses, microbiome-context-dependent disease, and modern multifactorial conditions; insisting on them mechanically can rule out real causal relationships.