Defending Abduction

Charles S. Peirce argued that, besides deduction and induction, there is a third mode of inference which he called "hypothesis" or "abduction". He characterized abduction as reasoning "from effect to cause", and as "the operation of adopting an explanatory hypothesis". Peirce's ideas about abduction, which are related also to historically earlier accounts of heuristic reasoning (the method of analysis), have been seen as providing a logic of scientific discovery. Inference to the best explanation (IBE) has been regarded as an important mode of justification, both in everyday life, detective stories, and science. In particular, scientific realism has been defended by an abductive no-miracle argument (Smart, Putnam, Boyd), while the critics of realism have attempted to show that this appeal to abduction is question-begging, circular, or incoherent (Fine, Laudan, van Fraassen). This paper approaches these issues by distinguishing weaker and stronger forms of abduction, and by showing how these types of inferences can be given Peircean and Bayesian probabilistic reconstructions. 1. Peirce on Abduction. Charles S. Peirce made a distinction between three modes of scientific reasoning already in his Harvard Lectures during the spring of 1865. Starting from Aristotle's doctrine of induction as the inference of the major premise of a syllogism (of the first figure), Peirce observed that there is "a large class of reasonings" that are neither deductive nor inductive: reasoning a posteriori to a physical hypothesis, or inference of a cause from its effect (W 1:180). This reasoning, which Peirce called Hypothesis, can be represented as the inference of the minor premise of a syllogism. Besides Aristotle, Peirce's inspiration and the term 'hypothesis' came from the 1800 edition of Immanuel Kant's Logic (W 1:451). This classification of inferences was elaborated in Peirce's Lowell Lectures in the fall of 1866, and published in the next year. In Peirce's series for Popular Scientific Monthly ten years later, this distinction was presented in the article 'Deduction, Induction, and Hypothesis' (1878). Peirce illustrated the two ways of inverting deductive arguments by the following example with a Barbara syllogism. Deduction is an inference of a result from a rule and a case: