Charles Sanders Peirce

Excerpt on Deduction, Induction, and Abduction

The most important extension Peirce made of his earliest views on deduction, induction, and abduction involved was to integrate the three argument forms into his view of the scientific method. As so integrated, deduction, induction, and abduction are not simply argument forms any more: they are phases of scientific methodology, as Peirce conceived this methodology. In fact, in Peirce’s most mature philosophy he virtually (perhaps totally and literally) equates the trichotomy with the three phases he discerns in the scientific method.

Scientific method begins with abduction: a conjecture or hypothesis about what actually is going on. Then, by means of deductive inference, conclusions are drawn from the hypothesis about other things that must obtain if the hypothesis is assumed to be true. These other things, it is hoped, can be experimentally tested-for. Finally, hypothesis-testing is performed by seeking experimentally to detect something that has been deduced to obtain from the hypothesis. The entire procedure of hypothesis-testing, and not merely that part of it that consists of arguing from sample to population, is called induction in Peirce’s later philosophy.

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