João R. Fett

Defeat is the loss of justification for believing something in light of new information. This Element mainly aims to work towards developing a novel account of defeat. It distinguishes among three broad views in the epistemology of defeat: scepticism, internalism, and externalism and argues that that sceptical and internalist accounts of defeat are bound to remain unsatisfactory. As a result, any viable account of defeat must be externalist. While there is no shortage of externalist accounts, the Element provides reason to think that extant accounts remain unsatisfactory. The Element also explains the constructive tasks of developing an alternative account of defeat and showing that it improves on the competition.

Faced with vivid cases of inferential knowledge to which false premises seem evidentially indispensable—knowledge-from-falsehood cases, or 'KFF cases'—some of us retreat from the traditional, Aristotelian view that only knowledge begets knowledge in reasoning. But KFF-ers are a minority in the debate over such cases. The epistemology of reasoning is still dominated by KDF-ers, those for whom, on close inspection, purported KFF cases turn out to be knowledge-despite-falsehood cases. Each group has its own warring factions. I belong with those who think that every KDF proposal on the market is hopeless, which saddles me with the fundamental problem for KFF-ers: the task of explaining why some false premises are knowledge-suppressing, or 'malignant', while others are knowledge-yielding, or 'benign'. Some have suggested that a satisfactory KFF view might be found within truth-tracking epistemologies, either a safety-based theory or a sensitivity-based one. I examine the hypothesis and conclude that it fails. I then turn to the defeasibility theory of knowledge, a theory that has been deployed by its chief architect, Peter Klein, in defense of a KDF stance, and argue that the desired benign/malignant distinction can be found within a properly formulated, non-Kleinian defeasibility theory.

Talk of ‘defeasible/nondefeasible reasoning’ by some of our leading epistemologists and logicians is misleading. It embodies conceptual confusion about epistemic defeasibility, fallibility, and monotonicity in influential accounts of inferential justification. As argued here, this form of deeply entrenched confusion has blurred the distinction between the concepts of fallibility and defeasibility under the guise of the seemingly benign synonymy between the labels ‘defeasible reasoning’ and ‘nonmonotonic reasoning.’ The careless employment of these labels has had a harmful effect on our understanding of inferential justification. Specifically, it has blurred the fundamental distinction between truth-preservation and justification-preservation in the relevant literature, thus harming the epistemology of reasoning at its core. We have been warned by Timothy Williamson against this kind of confusion, but the warning has gone unheeded. That warning is explained and amplified here on the basis of abundant textual evidence and the discussion of exemplary cases.