Probabilism reconsidered: Deference to experts, types of uncertainty, and medicines

Probabilist moral theologians held that, in situations of uncertainty, it is morally permissible for an expert to defer to an opinion regarded as less probable than his own (which he retains unchanged). Probabilism has been customarily taken to answer the question: "how should I act in circumstances of moral uncertainty?" I argue that originally it constituted an answer to the very different question: "what weight should experts assign to the opinions of their peers when providing advice to laymen?" Critics charged that medical cases show that probabilism is wrong. I analyze three attempts by probabilists to address this charge.