Evidential reasoning in historical sciences: applying Toulmin schemes to the case of Archezoa

This article is a study of the role and use of evidence in the evaluation of claims in historical sciences. To do that, I develop a "snapshot" approach to Toulmin schemas. This framework is applied to the case of Archezoa, an initially supported then eventually rejected hypothesis in evolutionary biology. From this case study, I articulate a philosophical analysis which criticizes Cleland"s "smoking gun" account of the methodology of historical sciences. I argue that Toulmin schemas are conceptually precise tools that allow for the building of enriched reconstructions of evidential reasoning. It displays and suggests three ways in which the construction and use of facts in historical sciences is theory-laden. Despite its inherent limits, TS are heuristically useful tools to identify epistemic moves that could be further investigated. It also sheds light on the positive roles of speculation in historical sciences. Finally, I argue that it provides a context-specific and individuated understanding of hypothesis evaluation in historical sciences. Overall, I think the application of Toulmin schemas to cases of evidential reasoning in historical sciences is a promising descriptive and heuristic tool for philosophers of science.