Cognitive scientists such as Keith Stanovich describe two classes of rationality. Instrumental rationality is defined as ‘the optimisation of someone’s goal fulfilment’, or, less technically, as ‘behaving so that you get exactly what you want, given the resources available to you’. Epistemic rationality, meanwhile, concerns ‘how well your beliefs map onto the actual structure of the world’. By falling for fraudulent mediums, Conan Doyle was clearly lacking in the latter.
