This collection of 17 essays, written by a group of eminent academics, is the product of the 9th Obligations conference, which brought together a vast number of private law enthusiasts in 2018 to debate the theme of “form and substance”. Each essay selected for the volume is of high quality on its own terms, and all are written with the clarity and insight that we have come to expect, following on from the conference's previous collections.

One might question how useful the collection's theme is as a tool for analysing the contributions to it. In a concluding piece offered in part as an overview, Kit Barker usefully lists 13 different interpretations of the theme (pp. 434–35), while, on the first page of the opening substantive contribution, Andrew Burrows suggests that it is “probably a distinction that is best avoided” because it can be understood in so many unrelated ways (p. 17). For present purposes, I shall heed that advice, and consider the essays along a spectrum split between two extremes: at one end are those papers that drill down into a narrow doctrinal issue, and, at the other, are those that defend much more general claims that cut across substantial swathes of private law.

Andrew Robertson's essay falls into the first camp. He attempts to show that all instances of equitable estoppel (with the possible exception of “estoppel by acquiescence”) are united by a single underlying principle: that where A induces an assumption in B that creates a risk of B suffering harm, and A is sufficiently responsible for that risk, A is required either to prevent, or to answer for, that harm. Similarly focused are the contributions by Jeannie Marie Paterson and Elise Bant (on misrepresentation), by James Goudkamp and Eleni Katsampouka (on punitive damages), and by Jason Neyers (on the tort of deceit). The two former papers adopt a comparative approach, contrasting styles of judicial reasoning across common-law jurisdictions, and come to similar conclusions: English law primarily relies on strict and settled rules, but is beginning to show a willingness to fall back onto deeper, more purposive arguments. In that respect, English courts are moving closer to their counterparts in other jurisdictions. Neyers, in contrast, is more normative in outlook. He advocates the abandonment of “loss” as an element of the cause of action in deceit, and suggests instead that what must be shown is “the non-consensual dispossession of a right” (p. 330). The latter is said to be a better fit with existing case law, and to avoid the difficulty that would be caused if the law were to require claimants to determine a precise moment at which they suffer loss.

Sitting more towards the middle ground of our two extremities are two contributions that cover a number of specific instances where a court is willing to look past initial appearances to inner reality in order to determine the legal effect of a given transaction. The contributions of Pey-Woan Lee and Birke Häcker on this topic dovetail nicely. Lee's chapter traces many examples – including tenancy, employment and financing agreements – and argues that wherever a court recharacterises such agreements, they unavoidably engage with policy, “weighing competing values and social goals” (p. 93). Where an agreement labelled a licence by the parties is characterised instead as a lease, this is done because of a “desire to give effect to relevant legislative policies” that govern leases – in particular, the goal of protecting vulnerable parties (p. 79). The main value that weighs against this sort of recharacterisation is that of party autonomy, and Häcker argues that, in some specific areas, courts would do well to give this value more weight. In particular, parties ought to be able to “grant someone a merely personal right to occupy premises for a certain duration at a stipulated rent” (p. 41). As the law presently stands, such a grant would be treated as creating an interest in the grantee that is of proprietary effect, and there seems no reason why this must be so.

Burrows also draws a distinction between outward appearance and inner reality, but his is a distinction of a different sort. He lists examples of “fictions” in private law, defined as “a rule or concept or line of reasoning that is used by judges but obscures their true reasoning” (p. 22, emphasis added). The central claim of Burrows’ essay is that many fictions are adopted in order to give the law a false sense of legitimacy, because they underplay the role of the judiciary, which may be to create law or to impose duties onto parties. Thus it is common to hear invocations of “parliamentary intention” when statutes are interpreted, or of “the intentions of the parties” when default rules of contract law are applied, even though the truth is that neither of these intentions exist.

The difficulty with Burrows’ argument is that it does not seem correct to think that all of the examples he lists are fictions, rather than unconvincing – but genuine – attempts to explain the law as it is found. Burrows might be right to argue that these attempts handily seem to imbue the law with an undeserved sense of legitimacy, but his central claim surely goes too far. It seems more accurate to say that invocations of false “intention” are the result of a temptation to try to explain legal rules as flowing from the consent of the parties or Parliament. If we know that a good reason for imposing a duty onto A is that A willed that duty into existence, it is tempting to try to explain that duty on that basis. If this can be done, it follows that the duty has good reason to exist – but this is surely not the only way in which we might make out such a claim. Burrows should be read as calling on readers to look beyond superficial explanations of legal rules, and to be more willing to try to demonstrate the law's legitimacy by offering deeper, and more intellectually satisfying, explanations of the law rooted in concerns other than the consent of the parties or Parliament.

Further along the spectrum are a number of essays that focus on specific issues only as a tool to defend more general claims that, if found to be convincing, have implications for areas of private law not explicitly discussed. Two writers who argue in this fashion in an attempt to demonstrate the particular value of stable rules are James Lee and William Swadling. With detailed reference to the duty of care in negligence and vicarious liability, Lee outlines a growing trend in English tort law towards rules of law that incorporate reference to policy considerations, and calls on courts to revisit the more determinate rules of the past. An interesting contrast might here be drawn with Man Yip's chapter, which makes the opposite argument in respect of equitable doctrine. She traces a similar trend towards more fact specific and evaluative decisions, but hopes that courts continue on that trajectory so that Equity might keep pace with increasingly diverse and complex human interactions.

Swadling criticises the dismissal of settled law on the grounds that it is overly technical, and its subsequent replacement with rules that supposedly better reflect “reality”. He fiercely criticises two recent decisions that have adopted this kind of reasoning: Shell UK Ltd. v Total UK Ltd. [2011] Q.B. 86 (where the Court of Appeal allowed a beneficiary under a trust to bring a claim for consequential loss against the negligent damager of trust property, so long as the trustee was joined to the action) and Menelaou v Bank of Cyprus UK Ltd. [2015] UKSC 66 (where the Supreme Court adopted a very wide view of the principle of unjust enrichment to allow a bank to subrogate to a lien over property that would not have been acquired had the bank not incorrectly believed that it would acquire a valid mortgage of the property).

In criticising Shell, Swadling is joined by Häcker and Ben McFarlane. At root, their issue with the case is that the court misunderstood the nature of a beneficial interest under a trust. Such an interest, it is argued, is not a form of ownership, but rather endows the beneficiary with a right that burdens the legal owner's title to the trust property – the owner comes under an obligation to exercise that right for the beneficiary's benefit. One interesting question that stands out while reading this persistent criticism is why the incompatibility of Shell with prior understanding of the nature of a trust does not place a burden on the interpreter of the law to produce a new understanding, that can account for both Shell and the body of case law that preceded it, rather than suggesting that Shell itself is wrongly decided.

McFarlane's discussion of the case is part of a much wider argument, that seeks to demonstrate that a division exists within private law between “primary rules that define the parties’ rights, and secondary rules that control, in favour of B specifically, A's acquisition or enforcement of rights” (p. 199). This division roughly tracks the split between rights that are “legal” and “equitable”. The beneficial interest under a trust, of course, is said to be one example of a secondary right. Others include the right that arises under promissory estoppel, which prevents the holder of a contractual right to payment from enforcing that right against the promisee, and the right that arises in a mistaken payor to restitution from the payee. McFarlane's analysis can add clarity in our understanding of the operation of many rules, and, if found convincing, serves as an important preliminary step to be taken before moving on to assess those rules.

Of the contributions of the most explicitly general sort, the essay most likely to garner significant attention is that by Robert Stevens. This piece picks up from Stevens’ earlier work, helping to make the case that the concept of “performance” (defined as the doing by A of some action for B that is accepted by B) and its reversal should be adopted as an organising idea in the law of restitution. The essay repeats many of the claims that Stevens has made previously (“The Unjust Enrichment Disaster” (2018) 134 L.Q.R. 574), but makes much clearer – and at much greater length – some vital theoretical claims that underpin Stevens’ project.

I would here note two gaps that Stevens ought to bridge in future work if he is to persuade readers to come round to his view. First, his most important claim – that private law obligations can only be properly justified by reference to reasons that are bilateral in nature, that apply to both parties the subject of the duty – ought to be positively defended. It is instead here asserted, alongside illustrations of commonly invoked reasons that are unilateral in nature (such as a concern to deter wrongdoers) that fail to convincingly justify certain private law duties (pp. 124–26). However, it appears, intuitively, to be the case that anything that shows a legal duty to be a “good thing” should count in its favour when it comes to assessing that duty. Without fuller exposition, we might well conclude that Stevens offers us no reason to think that obligations cannot be justified by reference to a collection of reasons that are unilateral in nature. Second, Stevens does not explain why it is that we need the concept of “performance” to ensure that the law is imbued with the necessary bilaterality. The law could, to take the example of a mistaken payment, hold that the payee must not only accept payment, but also have knowledge of the payor's mistake. Why is it that “performance” is bilateral enough such that the law ought to be concerned with its reversal? I suspect that Stevens’ answer lies in the fact that this is one bilateral concept that fits a substantial amount of case law, but it is hard to see how fit with existing law could count in favour of his claim that this is what the law ideally should be (p. 146).

Another wide-ranging theoretical piece that deserves a sizeable readership is by Dan Priel, who investigates “the philosophical foundations of doctrinal scholarship” (p. 165). The question of proper methodology in private law scholarship is one that has received too little attention, and Priel ought to be praised for tackling it head on. His focus is on two ideal types of inquiry into private law doctrine, which he terms “conceptualist” and “doctrinalist”. The former divines principles from an examination of the relationships between parties, and treats cases as possible illustrations of those principles; the latter starts firmly with the case law, and seeks to draw out principles internal to the law from those cases. Priel then goes on to assess the merits of each approach, and rejects conceptualism because it fails to align with legal practice and seems to close the academic study of law off from valuable insights coming from other disciplines. Doctrinalism fares better, but suffers from an inherent flaw in that, strictly followed, the law's rules would stagnate, failing to adapt to changing external forces.

One minor issue to raise here is that Priel's paper strikes me as a missed opportunity to demonstrate the value of publishing work as part of a collection of essays, rather than as a free-standing journal article. Within the collection is a wealth of concrete material, fresh in the reader's mind, on which Priel might have drawn to illustrate his arguments. This would have made his paper more impactful, and would have made reading the book as a single whole much more rewarding. This is characteristic of the main criticism that might be made of the collection: with a few exceptions, the essays within it are largely standalone pieces that do not hugely benefit from sitting alongside each other. Individually, however, those pieces undoubtedly make important contributions to private law scholarship, and they deserve to be widely read.