Inference to the Best Explanation

Inference to the best explanation (IBE), also called abductive inference, is a mode of reasoning in which one infers the truth of a hypothesis because it provides the best available explanation of the evidence. IBE is widely used in science, medicine, and law: a doctor infers a diagnosis because it best explains the symptom cluster; a physicist infers a particle because it best explains the collision tracks; a jury infers guilt because it best explains the physical evidence. The principle is attributed to C.S. Peirce under the name 'abduction' and was given its modern formulation by Gilbert Harman. IBE is the primary epistemic engine of scientific realism — it is the argument that licenses belief in unobservable theoretical entities on the grounds that positing them provides the best explanation of observable phenomena. The principle faces two foundational challenges: the underdetermination objection (the data may be equally well explained by multiple incompatible hypotheses, leaving IBE silent on which to infer), and the question-begging objection (IBE selects the 'best' explanation using criteria — simplicity, unity, explanatory depth — whose connection to truth has not been independently established). Whether IBE is a reliable guide to truth, or a heuristic that merely tracks our cognitive preferences for certain explanatory structures, is unresolved in epistemology.