Rik Peels and Martijn Blaauw offer two key observations in their introduction to The Epistemic Dimensions of Ignorance. The first is that epistemologists have largely ignored ignorance. The only exception they note to this rule is the cameo role ignorance sometimes plays in debates about radical scepticism; generally speaking, ignorance is ‘virtually absent’ from the recent epistemological literature (1). The second observation, moreover, notes that this neglect also runs the other way: philosophers who have been interested in ignorance generally ignore epistemology. Ignorance itself is far from virgin philosophical territory, playing a prominent role in Rawlsian political philosophy, debates about blame and moral culpability, and the philosophy of religion, amongst others. However, none of these other domains pay much attention to the epistemological dimensions of ignorance.

The purpose of this collection, Peels and Blaauw claim, is to break down the barriers that have arisen between these two areas of philosophical inquiry, and thus to start drawing out the vast array of ways in which ignorance might feature in epistemological investigation. Such investigations, they suggest, might look into the fundamental nature of ignorance, and ask what ignorance actually is. They might explore whether or not there are different types of ignorance, or whether it comes in degrees. Or they might consider how, if at all, ignorance relates to other fundamental epistemological concepts, such as knowledge or justification (2–3). The essays assembled discuss these issues and more, and the result is a volume that is invariably interesting and often of considerable scholarly merit, though perhaps not always as epistemologically innovative or adventurous as one might have hoped. In this review I offer a brief summary of the central arguments undertaken in the various essays, before ending with some comments about this latter domain of assessment.

The papers within this collection comprise three sections. The first, and longest, section lays the conceptual groundwork, posing questions about the fundamental nature of ignorance. Pierre Le Morvan and Rik Peels get us under way, reprising an argument they had within the pages of Philosophia about what it is we are ignorant of when we are ignorant. The ‘Standard View’ on this issue maintains that ignorance is the lack or absence of knowledge. The ‘New View’, meanwhile, claims that ignorance is the lack or absence of true belief. There are no knockout blows here, and nor are any attempted; the authors' stated aim is not to convince the reader of either view, but merely to assemble some of the arguments that proponents of either view might draw upon to further their cause. The rest is left up the reader. The paper largely stays within the bounds of their earlier discussion in Philosophia, but for those who are unfamiliar with this debate it is a helpful overview of a central controversy that resurfaces in several of the subsequent chapters.

Nikolaj Nottelman's builds upon this platform in the following chapter, initiating discussion on a number of issues about the nature of ignorance that generally, though not always, runs orthogonal to the debate between the New and Standard views. Nottelman's discussion covers a lot of ground, starting by delineating and defining four varieties of ignorance: factual ignorance, ignorance of entities, erotetic ignorance (or ignorance of the answers to questions), and practical ignorance. None of these can be straightforwardly reduced to any of the others; the case is strongest for reducing erotetic ignorance to factual ignorance, provided we are happy (as Nottelman appears to be) to assume that erotetic knowledge reduces to factual knowledge, but the intellectualist assumption underpinning a reduction of practical to erotetic ignorance – namely, that practical ignorance is merely ignorance of the answer to a question about how to φ skilfully – is more controversial. He closes the chapter with discussion of two further issues: degrees of ignorance, and the significance of higher-order ignorance.

A number of these issues are taken up by Berit Brogaard in her chapter, though her central argument is against the Standard View of ignorance as a lack of knowledge. This argument draws upon ‘evidence from ordinary language’ (57), where, Brogaard argues, ‘is ignorant’ functions grammatically and semantically differently from ‘knows’. Most significantly, she claims that ‘is ignorant’ is a gradable expression: whilst one either knows that p or doesn't know that p, one can be quite ignorant of that fact that p, very ignorant of the fact that p, or more ignorant of that fact that p than someone else is. So, whilst she accepts that ignorance of a fact does entail a failure to know that fact, ignorance's gradability means that one can fail to know a fact without being completely ignorant of it. I suspect Brogaard's appeal to ordinary language here is more controversial than she acknowledges. Elsewhere in the volume both Nottelman (52) and Erik J. Olsson and Carlo Proietti (85) claim that factual ignorance does not come in degrees, and some of the phrases that Brogaard presumes to be felicitous, such as ‘John is more ignorant of the fact that Mary came than Dennis is’ (61) or ‘For someone who is normally very attentive, John was quite ignorant of the fact that Mary was there’ (69), do strike me as slightly jarring. However, ignorance is plausibly gradable in some respects, and Brogaard's use of this asymmetry to suggest that ‘is ignorant’ is the complement of the similarly gradable ‘is knowledgeable’, rather than of ‘knows’, represents an insightful interjection to the debate.

Olsson and Proietti's own chapter analyses ignorance along with a related concept: doubt. They do so by employing the tools of formal epistemology, and in particular the framework of possible worlds, though their discussion is sympathetic and shouldn't pose much difficulty to those unfamiliar with these methodologies. The conclusion of their inquiry is that ignorance as to whether X is a state in which both X and not-X are ‘accessible’ to the agent; they neither know that X, nor know that not-X. Doubt, meanwhile, is a ‘stronger kind of indecision’ about these alternatives (91). This is filled out in two, possibly compatible, ways: either that the relevant alternatives are both, or all, ‘seriously possible and attended to’ (92), in the sense that they are all afforded maximum plausibility; or that the question as to whether X is on the agent's ‘research agenda’ (93). This sheds light not only on the relation between ignorance and doubt, but also on their relation to knowledge and belief respectively: if this analysis holds, ignorance and doubt are not the mere negations of knowledge and belief.

The next three chapters discuss ignorance in relation to contemporary debates in epistemology. First are two chapters, from Michael Blome-Tillman and Jessica Brown, that explore ignorance's familiar role as the menacing presence underpinning sceptical arguments. Blome-Tillman provides a helpful overview of epistemic contextualism as a response to radical scepticism, defending the position from the objections that it is, properly speaking, a linguistic view with minimal epistemological significance, and that ‘know(s) p’ differs in linguistic properties from other, more familiarly context-sensitive expressions. Brown, meanwhile, considers a sceptical worry that arises from anti-intellectualist arguments in which whether a subject knows p depends ‘not only on traditional truth-conducive factors, but also on the stakes for her’ (114). The worry arises from the fact that different people, and people at different times, vary in their epistemic positions and their stakes, such that someone who knows that p in a low stakes context might not be able to transmit that knowledge, either via testimony or through memory, to a high stakes context. Brown tries to downplay this worry, suggesting that speakers and hearers often do display the appropriate stakes-sensitivity that is needed to preserve these valuable sources of knowledge.

Whilst ignorance itself somewhat shrinks from view in Blome-Tillman and Brown's chapters – with the exception of Blome-Tillman's interesting comments on the potential context-sensitivity of ignorance, it essentially reprises the background role it has long played in worries about scepticism – it returns to the forefront in Duncan Pritchard's exploration of epistemic value. Ignorance is, Pritchard notes, a negative epistemic standing, but it is not necessarily a disvaluable epistemic standing, in the sense of having a kind of disvalue that is distinctively epistemic. This is because certain forms of ignorance can be conducive to the ultimate epistemic goals of acquiring truths and avoiding falsehoods. Sometimes focussing on the acquisition of a single truth of great substance – one that, as Pritchard puts it, has more ‘content’, in that it captures more of the truth (139–140) – is an epistemically valuable course of action, even if that requires remaining ignorant about a vast realm of truths that are less epistemically significant. Thus, in these cases ignorance is epistemically valuable.

The final section takes a somewhat broader understanding of the relevance of ignorance to epistemology, exploring issues that ‘go beyond the purely cognitive’ and are ‘not confined to the epistemic dimensions’ (9). Justin McBrayer's chapter provides a fascinating survey both of the different ways in which ignorance is put to work in religious theorising and the ways in which it's incorporated into religious life. At times it feels like a bit of a stretch to describe this, as Peels and Blaauw do, as ‘religious epistemology’ (9); in fact, many of the arguments explored, such as appealing to human ignorance to counter the argument from evil or to divine ignorance to preserve human freedom in the face of worries about pre-destination, seem to fall more comfortably under the second kind of argument discussed in the introduction: arguments from elsewhere in philosophy that discuss ignorance without touching upon epistemology. However, this is not always the case, and this chapter does also provide us with one of the most striking illustrations of the differences between the Standard and New Views of ignorance. If God exists but a lack of evidence means we are not justified in believing this, then those who endorse, with Le Morvan, the Standard View that ignorance is a lack of knowledge must maintain that even theists are ignorant of God's existence. Those who adopt Peels’ New View and maintain that ignorance is simply the lack of true belief, however, are not committed to this conclusion (144).

The final two chapters, from Miranda Fricker and José Medina, introduce one area where epistemologists have paid significant attention to ignorance; namely, the important work done by feminist epistemologists and epistemologists of race on the kind of entrenched and motivated ignorance that often characterise unjust and stratified societies. Fricker's chapter explores this through the lens of her work on epistemic injustice, examining how two forms of epistemic injustice – testimonial and hermeneutical – contribute to the ‘preservation of ignorance’ (160). In the course of this discussion she defends her account of hermeneutical injustice from the claim that it does not accommodate the possibility of localised interpretive practices that marginalised groups develop to compensate for inadequacies in a society's privileged set of meanings, before searching for overlap between this phenomenon and the phenomenon of what Charles Mills has called ‘white ignorance’ (see e.g. ‘White ignorance’ in Race and Epistemologies of Ignorance, edited by Sullivan and Tuana). Medina's chapter focuses on ignorance and racial insensitivity, developing an account of the latter in terms of numbness: ‘numbness to the perspectives of racial others and their experiences’ (181). This results in forms of ignorance about racial others, about their lives and experiences, that are active, that occur at a meta- as well as an object-level, and that are typically self- as well as other-directed. Medina then begins the tricky work of developing an account of epistemic responsibility, both for individuals but also, and crucially, for collectives, that is a precondition for the other social responsibilities we have.

To what extent do Peels and Blaauw succeed in their stated aim of putting ‘the notion of ignorance on the epistemological agenda’ (6)? One's answer to this question will in part, I think, depend upon what one takes the epistemological agenda to be. Early on in their introduction, Peels and Blaauw distinguish between two conceptions of epistemology: a narrow one, in which it is understood as ‘the study of knowledge and justified belief’; and a broad one, in which it is understood as ‘the study of issues having to do with the creation and dissemination of knowledge’ (1). They go on to indicate sympathy with the broader conception when they defend the epistemological credentials of their project, noting how ‘the scope of epistemology has significantly broadened’ beyond a mere focus on knowledge in recent years (3), and chapters on epistemic value, epistemic injustice, and collective epistemology demonstrate a willingness at times to put this sympathy into practice. However, these chapters were amongst the exceptions. More often than not, this collection gave the impression of working within a conception of epistemology in which knowledge remains the fundamental unit of analysis, and its scope felt quite narrow as a consequence.

This narrowness could, perhaps, be seen in the strength of Peels and Blaauw's initial claim about the neglect of ignorance. Ignorance has largely been ignored by recent epistemologists, it is true, but to claim that ‘the only area that ignorance enters the discussion is in debates on radical scepticism’ (1, emphasis added) is to neglect some valuable work done on the topic by feminist epistemologists, social epistemologists, and epistemologists of race (for example, Race and Epistemologies of Ignorance, edited by Sullivan and Tuana, and A Defense of Ignorance, by Cynthia Townley). More transparently, however, it can be seen in the focus of the various chapters assembled, the majority of which explore, in one way or another, the relation between ignorance and knowledge (or, perhaps, true belief). Knowledge, of course, remains the central focus of much epistemology, and repeatedly returning to this theme did allow for interesting points of conversation to develop between the chapters. Nonetheless, there were a whole range of omitted topics which have recently risen to epistemological prominence and that felt ripe for discussion. For example, can we be ignorant of understanding, as well as knowledge? What is the connection between ignorance and trust? And how, if at all, does ignorance relate to epistemic virtues and vices? No volume can be expected to explore every area of interest, and as I've indicated this one is by no means methodologically or thematically homogenous. However, to fully illustrate ignorance's relevance to the contemporary epistemological agenda I would have liked it to expand a bit further into these new epistemological directions.

This disappointment notwithstanding, I believe Peels and Blaauw have done epistemology a considerable service with this collection. They have recognised an important lacuna in the field, argued cogently that it is one epistemologists should be interested in filling, and assembled a collection of essays that begin to do so. The various contributions are clearly written and philosophically rich, mapping the terrain of a range of important debates and prompting numerous new directions for research. For epistemologists interested in ignorance, this collection will be a go-to text for years to come.