Inference to Best Explanation (IBE) is a method of reasoning in which one infers, from a body of evidence, the truth of the hypothesis that would, if true, provide the best explanation of that evidence. The term was introduced by philosopher Gilbert Harman in 1965, though the underlying pattern of reasoning-sometimes called “abduction,” following Charles Sanders Peirce-has a longer history in philosophy of science. IBE is typically contrasted with deductive inference, which guarantees its conclusion given true premises, and with simple inductive generalization, which extrapolates from observed instances to a general rule without invoking explanatory considerations. What counts as making one explanation “better” than its rivals-simplicity, scope, coherence with existing theory, fit with the evidence-is itself a matter of dispute among philosophers; see inference-to-best-explanation-criteria-of-explanatory-virtue-debate.

IBE is widely used as a description of reasoning in both everyday and scientific contexts-diagnosing a mechanical fault from its symptoms, or a physician inferring a disease from a set of presenting signs are commonly cited examples. In philosophy of science, IBE has played a central role in debates over scientific realism, where it is invoked to argue that the explanatory and predictive successes of mature scientific theories give reason to believe those theories are at least approximately true. Critics have raised several persistent objections: that IBE requires an antecedent ranking of candidate explanations, which risks circularity or arbitrariness; that the explanation judged “best” among those actually conceived may not be the true one (“the best of a bad lot” objection, associated with Bas van Fraassen); and that explanatory and epistemic virtues (such as simplicity) may track human cognitive preferences rather than truth. IBE also figures prominently in the Underdetermination debate, since proponents of IBE often argue that explanatory considerations can break ties between empirically equivalent theories, while critics of IBE see this as smuggling in unjustified metaphysical preferences. The dispute over heliocentrism is frequently cited in this connection; see Heliocentrism - Philosophy of Science Viewpoint for treatment of IBE-related arguments in that historical episode.

• Realist viewpoint - IBE is a reliable, truth-conducive form of inference, and its successful track record in mature sciences licenses belief in the (approximate) truth of well-confirmed theories. See inference-to-best-explanation-scientific-realist-viewpoint.
• Skeptical/instrumentalist viewpoint - IBE at most justifies belief in the empirical adequacy of a theory, not its literal truth, since explanatory virtues are not reliable guides to truth. See inference-to-best-explanation-constructive-empiricist-viewpoint.
• Bayesian reductionist viewpoint - Apparent IBE reasoning is best reconstructed as ordinary Bayesian conditionalization, with “explanatoriness” functioning, if at all, only insofar as it tracks prior probability; IBE has no independent epistemic force. See inference-to-best-explanation-bayesian-reductionist-viewpoint.
• Pluralist/contextualist viewpoint - IBE is reliable in some domains and disciplines but not others, depending on the maturity of background theory and the availability of a well-specified space of competing explanations. See inference-to-best-explanation-contextualist-viewpoint.
• Eliminativist viewpoint - So-called explanatory inference plays no legitimate evidential role distinct from likelihood and prior probability considerations already captured by standard confirmation theory; “best explanation” talk is a heuristic gloss with no inferential force of its own. See inference-to-best-explanation-eliminativist-viewpoint.

• Dispute over whether IBE-based arguments for scientific realism beg the question against rivals such as constructive empiricism, since the legitimacy of IBE as a form of inference is precisely what is contested between the two camps. See inference-to-best-explanation-realism-debate-controversy.

• History: inference-to-best-explanation-history
• Debate: inference-to-best-explanation-criteria-of-explanatory-virtue-debate
• Viewpoint Debate: inference-to-best-explanation-realist-empiricist-viewpoint-debate
• Related Main Topic: Underdetermination
• Related Main Topic: Scientific Realism
• Related Main Topic: abduction

1. Gilbert Harman, “The Inference to the Best Explanation,” *Philosophical Review* 74, no. 1 (1965): 88-95.
2. Peter Lipton, *Inference to the Best Explanation*, 2nd ed. (London: Routledge, 2004).
3. Bas C. van Fraassen, *The Scientific Image* (Oxford: Oxford University Press, 1980).
4. Igor Douven, “Abduction,” in *The Stanford Encyclopedia of Philosophy*, ed. Edward N. Zalta and Uri Nodelman, Fall 2021 ed., Stanford University, last modified August 18, 2021, https://plato.stanford.edu/archives/fall2021/entries/abduction/.