An anthology of one introduction and ten original essays for advanced students and researchers on an increasingly popular topic of philosophical discussion, Disagreement is a volume with a name that matches its contents. The essays, for the most part, situate themselves squarely in the epistemological domain. In terms of length, the contributions range from twelve pages to forty pages, not including the particularly lengthy essay of Thomas Kelly, entitled ‘Peer disagreement and higher-order evidence’, which is sixty-four pages long.

Disagreement begins with an introduction by the editors and the introduction begins with something which we see much of throughout the book, namely, an attempt to get to grips with disagreement by formulating the philosophical problem and making explicit important assumptions. The notion of disagreement among intellectual peers, we are told, can involve cases where peers differ on the best conclusions to draw from evidence and even on what the evidence is (or who has the most evidence). So what is to be done? Do parties to a dispute revise their beliefs or do they remain justified in their own beliefs? If there is need for revision, is it by all disputing parties or just some? The types of assumption that are needed to make the problem interesting include restrictions on the term ‘peer’. Intellectual peers are those who are in the same league as each other regarding availability of information and possession of intellectual virtues. Disputes between intellectual peers become interesting when the disputes do not arise out of basic errors of judgement or thought and when multiple positions are not valid.

After a helpful start to the anthology, we are reminded of the relevance of disagreement to the philosophy of religion. In the first line of ‘We're right. They're wrong’ (chapter 1), a contribution by Peter van Inwagen, it is suggested that general discussion on disagreement arose from discussion of religious disagreement. Van Inwagen focuses on defining and explaining three forms of alethic exclusivism, that is, three forms of the view that only one thesis on a matter is true to the exclusion of all the opposing theses. The varieties of exclusivism are termed ‘weak’, ‘strong’, and ‘very strong’, with the difference being the attitude to those who maintain rival theses. So, a weak exclusivist is an alethic exclusivist that believes peers from opposing camps can be rational; a strong exclusivist is an alethic exclusivist who believes a peer from a opposing camp is irrational if they enjoy the same epistemic situation; and a very strong exclusivist is an alethic exclusivist who believes a peer from an opposing camp is always irrational whatever their epistemic situation.

Van Inwagen rejects such self-gratifying reasons for peer disagreement as the unavailability of a key insight or an advantageous neural quirk. Instead he wonders how two peers (namely, David Lewis and himself on the problem of free will) can disagree and yet both remain rational. Van Inwagen determines that this is just the way it is. This is not entirely satisfying to the reader and one would wish to invite more discussion on the type of rationality that permits this conclusion. Furthermore, given that the problem of disagreement is a problem of confidence, Van Inwagen doesn't seem to have done anything to address this. It doesn't make one any more confident in their informed, yet contentious, beliefs just if they know that disagreement is normal and oftentimes practically irresolvable.

In chapter 2, ‘Belief in the face of controversy’, Hilary Kornblith engages with other writers (mainly Kelly and Elga) to argue that the significance of epistemic disagreement depends on the subject. In disciplines like mathematics, logic, and science, our experience teaches us to take seriously consensus or lack of consensus among experts. On the other hand, the history of philosophy teaches us no such thing and we should not be under the pretence that it does. Kornblith even says that our beliefs on disputed matters are not even epistemically justified (p. 45) and in general recommends ‘epistemic modesty’ (p. 52) along with the hope of philosophical progress.

In chapter 3, ‘Persistent disagreement’ by Catherine Elgin, we are reminded that belief is not voluntary. Recommendations of what a rational person should believe in the light of significant disagreement should take this fact into account. A person cannot just suspend his belief or modify his belief at will. However, if by ‘belief’ we mean ‘acceptance’ – as we often do – then it is reasonable to offer recommendations about what we should and should not accept. In chapter 4, ‘Rational disagreement defended’, Earl Conee finds that he cannot make plausible the principle that disagreeing epistemic peers with the same evidence cannot all be justified. Because people have different perspectives and different evidence for their beliefs they can all be justified in some cases of disagreement. In other words, it is not correct to maintain the unique rationality of a single perspective. In chapter 5, ‘You can't trust a philosopher’, Richard Fumerton makes the problem of disagreement all too clear by touching on a few raw nerves. Apparently, ‘the foreign policy of the United States over the last hundred years or so has been something of which we should be very proud’ (p. 100). Although there are cases where one can reasonably believe despite the disagreement of peers, in philosophical contexts the unreliability of philosophers cannot be ignored.

In chapter 6, ‘Peer disagreement and higher-order evidence’, Thomas Kelly develops the argument of an article published in 2005, changing his mind about some matters. Kelly usefully distinguishes between five different responses to the problem of disagreement. The most important of these responses for Kelly's purposes are the ‘Equal Weight View’ (the view that in a case of peer disagreement one should give equal credence to the rival belief as to one's own belief) and the ‘Total Evidence View’ (the view that the justification of one's belief in a case of peer disagreement is related to one's total evidence). Kelly's discussion is aimed at showing how the latter position is preferable to the former. After all, sometimes we have to consider not just the evidence immediately relevant to a dispute; sometimes the opinions of peers also count as evidence to be considered! As previously mentioned, the length of this contribution makes it particularly prominent in the volume and a patient reader will be rewarded. However, as Kelly admits in his closing sentences, the proposed view requires enhancement so that it does not succumb to acknowledging ‘dialectical’ evidence as genuine. The point being made is that the temptation to reject a rival's opinion on the grounds that he has incorrectly assessed the evidence (thus disqualifying himself from being my epistemic peer) must be resisted.

In chapter 7, ‘How to disagree about how to disagree’, Adam Elga says that reconciliation of conflicting beliefs at first seems like a good idea. However, when this strategy is applied to disagreement about disagreement we realize that the idea is self-refuting. In chapter 8, ‘Epistemic relativism and reasonable disagreement’, Alvin Goldman addresses a topic of considerable importance to the philosophy of disagreement. After all, if a matter can be resolved in more than one way then more than one party to a dispute can be correct. Goldman argues for a respectable form of relativism which he claims does not collapse into nihilism. According to Goldman the implication of ‘objectivity-based relativism’ for reasonable peer disagreement (in cases where there is agreement over what constitutes evidence) is that peers can take differing attitudes to a body of evidence because they can reasonably disagree on the type of justification they seek for their beliefs.

In chapter 9, ‘The moral evil demons’, Ralph Wedgwood argues that moral disagreement is due to differences in pre-theoretical moral intuition. Because disputants have different moral intuitions at a pre-theoretical level they have different fundamental moral principles. When it comes to deciding the correct course of action on a given issue, these differences manifest themselves. But it is not enough for disputants over an issue of morality to suspend judgement. Rather, suggests Wedgwood, we should primarily be committed to trusting our own moral intuitions while not dogmatically dismissing those who disagree as irrational. Noticeable, in this contribution of seven sections, is that even in the fifth section the author is still presenting assumptions and focusing his contribution. A reader may have to read the essay a few times to be able to appreciate its argument fully.

Chapter 10, ‘Disputing about taste’ by Andy Egan, is the final chapter of Disagreement. Egan's main focus is to identify a number of features of ‘defective’ disputes about matters of taste, that is, disputes about taste which are not to be taken too seriously.

Disagreement is a straightforward anthology. There is no dialogue between the contributors (although I did spot one cross-reference on p. 54) and there is no conclusion. The essays were completed in 2007 and 2008, but bringing them to print met with some delay. One of the main features of the book which catches the attention is the extent of introductory material which is repetitive. It must be said that this is understandable given that all contributors are concerned to formulate the issue they are engaging with and that the contributions are, ultimately, all stand-alone contributions. The repetitive introductory material is also understandable given the relative youth of the subject at hand. Nevertheless, reading the book from cover to cover may require a good deal of commitment. Furthermore, on the readability of the book, it can also be noted that the depth of the contributions ensures that they demand more attention than that which can be offered to them on a daily commute – although we would rarely expect anything less.

Although clearly not an introductory text, Disagreement does succeed in acquainting the reader with the key positions in the philosophy of disagreement as well as the key terminology. There do, however, remain a few gaps. Perhaps more could have been made of the problem of disagreement being (in essence) a problem of confidence. As far as I can tell, the only mention of confidence can be found in the introduction. Also, little was made of a distinction which can be drawn between disagreement over correct inference (from shared premises) and disagreement over premises themselves. Wedgewood's contribution is somewhat of an exception to this, although not entirely. It seems that were the nature of disagreement more thoroughly identified then the consequences of it would also be more thoroughly identified.

There are now over one hundred articles, scattered in journals and anthologies, which engage with the philosophy of disagreement. However, to the best of my knowledge, Disagreement is the only anthology dedicated to the philosophy of disagreement. Indeed, there are hardly any book-length studies on the subject. For this reason, Disagreement is set to be a key reference for all those deeply interested in this gripping topic.