Good conversations are one of the great joys of life. Online (social media) ‘conversations’ rarely seem to make the grade. In this paper I use some tools from philosophy in an attempt to illuminate what might be going wrong.

In this paper I argue that epistemically normative claims regarding what one is permitted or required to believe (or to refrain from believing) are sometimes true in virtue of what we owe one another as social creatures. I do not here pursue a reduction of these epistemically normative claims to claims asserting one or another (ethical or social) interpersonal obligation, though I highlight some resources for those who would pursue such a reduction.

Externalism is the thesis that some propositional attitudes depend for their individuation on features of the thinker's (social and/or physical) environment. The doctrine of self-knowledge of thoughts is the thesis that for all thinkers S and occurrent thoughts that p, S has authoritative and non-empirical knowledge of her thought that p. A much-discussed question in the literature is whether these two doctrines are compatible. In this paper I attempt to respond to one argument for an incompatibilist conclusion, Boghossian's 1989 ‘Memory Argument.’

Politeness in conversation has epistemic costs, in that it saps conversational silence of its capacity to signal assent. Whether these costs are outweighed by the obvious social benefits of politeness is not a question we pursue here.

Elsewhere I and others have argued that evidence one should have had can bear on the justification of one's belief, in the form of defeating one's justification. In this paper, I am interested in knowing how evidence one should have had (on the one hand) and one's higher-order evidence (on the other) interact in determinations of the justification of belief. In doing so I aim to address two types of scenario that previous discussions have left open. In one type of scenario, there is a clash between a subject's higher-order evidence and the evidence she should have had: S's higher-order evidence is misleading as to the existence or likely epistemic bearing of further evidence she should have. In the other, while there is further evidence S should have had, this evidence would only have offered additional support for S's belief that p. The picture I offer derives from two “epistemic ceiling” principles linking evidence to justification: one's justification for the belief that p can be no higher than it is on one's total evidence, nor can it be higher than what it would have been had one had all of the evidence one should have had. Together, these two principles entail what I call the doctrine of Epistemic Strict Liability: insofar as one fails to have evidence one should have had, one is epistemically answerable to that evidence whatever reasons one happened to have regarding the likely epistemic bearing of that evidence. I suggest that such a position can account for the battery of intuitions elicited in the full range of cases I will be considering.