A defeater is, very broadly, a consideration that reduces or completely takes away justification from a subject’s belief about a certain proposition. According to a widely endorsed view, justifiers and defeaters require evidential support. However, a number of philosophers argue that unjustified beliefs can serve as defeaters as well. Call the former type of defeater an ‘evidential defeater’ and the latter a ‘doxastic defeater’. Doxastic defeaters are highly controversial. First of all, they seem to be flatly incompatible with evidentialism. Moreover and more alarmingly, if we accept that unjustified beliefs can be defeaters, we have to accept that unjustified beliefs can serve as justifiers as well. A further unwelcome implication is that epistemically irresponsible subjects could immunise themselves from defeat by generating their own defeater-defeaters. Problems like these have led philosophers to reject doxastic defeaters altogether. This paper argues that doxastic defeaters are intelligible given a dualistic conception of rationality.

I raise some questions about Jeremy Fantl's The Limitations of the Open Mind. I ask what type of applied epistemology Fantl's book represents, whether there might be a better conception of open-mindedness than the one he embraces, and whether he is correct that someone's being an amateur makes it easier for their knowledge to survive the dismissal of relevant counterarguments.

The child objection is a major challenge for reductionism, which requires hearers to have positive reasons for testimonial justification. However, it has been pointed out that anti-reductionism, which requires only the absence of negative reasons, or defeaters, suffers from the same kind of problem. The child objection presupposes the empirical thesis that “children do not have the capacity to consider reasons,” but the plausibility of this assumption may be revealed by developmental psychology research on selective trust. This paper uses recent epistemological studies as a guide to narrow down the types of defeaters that children are required to consider, and then clarifies what kind of reasons various experiments can be said to test the ability to consider, and in what sense children who pass the test can be said to be “considering” reasons. In doing so, we clarify the scope and limits of the implications that selective trust studies can have for reductionism and anti-reductionism. We then suggest what future psychological research is desired from an epistemological interest to go beyond the current limitations.

This paper argues for the existence of a certain type of defeater for one’s belief that P—the presence of social incentives not to share evidence against P. Such pressure makes it relatively likely that there is unpossessed evidence that would provide defeaters for P because it makes it likely that the evidence we have is a lopsided subset. This offers, I suggest, a rational reconstruction of a core strand of argument in Mill’s On Liberty. A consequence of the argument is that on morally and politically laden issues in particular, a high degree of doxastic openness might be appropriate.

Christian apologists argue that the testimony of the miracles of Jesus provide evidence for Christianity. Hume tries to undermine this argument by pointing out that miracles are said to occur in other religious traditions and so miracles do not give us reason to believe in Christianity over the alternatives. Thus, competing miracles act as an undercutting defeater for the argument from miracles for Christianity. Yet, before Hume, Locke responds to this kind of objection, and in this article I explain and defend his response. In short, Locke argues that God will ensure that there is more evidence for Christianity (if true) and this greater evidence is an undercutting defeater for Hume's competing miracles defeater (i.e. it is a defeater-defeater). If so, then, as Locke argues, competing miracles do not weaken the evidence from miracles for Christianity.

In a recent paper in this journal, Joshua Blanchard has identified a novel problem: the problem of unwelcome epistemic company. We find ourselves in unwelcome epistemic company when we hold a belief that is also held mainly or most prominently by those we regard as morally or epistemically bad. Blanchard argues that some, but not all, unwelcome epistemic company provides higher-order evidence against our belief. But he doesn't provide a test for when company is unwelcome or a diagnosis of why it is unwelcome. I provide both. On my disjunctive test, unwelcome epistemic company provides us with a defeater when either there is a match between the content of the belief and the properties that make our company unwelcome, or there is reason to suspect that the belief arose via a shared, unreliable, causal process.

Influential cases have been provided that seem to suggest that one can fail to have knowledge because of the social environment. If not a distinct kind of social defeater, is there a uniquely social phenomenon that defeats knowledge? My aim in this paper is to explore these questions. I shall argue that despite initial appearances to the contrary, we have no reason to accept a special class of social defeater, nor any essentially social defeat phenomenon. We can explain putative cases of social defeat with our existing epistemological apparatus.