In Charles Sanders Peirce's methodology, abduction, deduction, and induction are three distinct modes of reasoning that together form a comprehensive approach to scientific inquiry and the development of knowledge.
Abduction: This is the process of forming an explanatory hypothesis. It is the reasoning that involves generating a plausible theory or explanation for a given set of observations. Peirce considered abduction to be the starting point of scientific inquiry, where one seeks to identify a hypothesis that could explain the surprising facts. It is often described as the process of "inference to the best explanation."
Deduction: Once a hypothesis is formed through abduction, deduction is used to derive logical consequences from the hypothesis. It involves working out the implications of the hypothesis to determine what should be observed if the hypothesis is true. Deductive reasoning is concerned with testing the internal consistency and logical structure of the hypothesis.
Induction: This is the process of testing the hypothesis through empirical observation and experimentation. Induction involves gathering data and evidence to determine whether the predictions made through deduction hold true in reality. It is the method of confirming or disconfirming hypotheses by observing whether the expected outcomes occur.
In Peirce's view, these three forms of reasoning work in a cycle. Abduction generates hypotheses, deduction clarifies and predicts consequences, and induction tests these predictions against empirical data. This cyclical process allows for the refinement of theories and the advancement of knowledge. Peirce emphasized that scientific inquiry is iterative, with each mode of reasoning playing a crucial role in the development and validation of scientific theories.