It has got to be one of the paradoxes of analysis that the more familiar something gets, the greater the odds against its clear understanding become. “Legal validity” is a case in point. The notion is ubiquitous. Contracts, rules, IDs and passports are just some of the myriad things of which, validity and invalidity are predicated. Yet, despite its ubiquity – possibly, because of it – legal philosophers have not got around to systematically examining what legal validity is. This is not to suggest that getting validity right is not crucial. Quite the opposite. Matters impinging on life and liberty are routinely settled on the basis that something is valid, or in other words, “OK” to do. Here, as we are to learn from Köpcke, lie the etymological roots of validity or “OK-ness” – in the Latin valere, which means health, strength or fitness. The two books offer a rich and valuable – value too happens to be rooted in valere – study that addresses this gap in the literature. Between them, the books cover an impressively wide terrain not just methodologically, but also chronologically (and linguistically). They show how legal theory and legal history can be deftly brought together to yield mutually illuminating insights. Legal Validity: The Fabric of Justice emerging from a doctoral thesis which went on to win the triennial “European Legal Theory Award” offers an account of “legal validity” in the manner of analytic legal philosophy. A Short History of Legal Validity and Invalidity: Foundations of Private and Public Law offers a historical account of the origin of the “technique” of validity from Roman law down to our times. While the two books are best read together, each of them is a self-contained unit with essential insights from each weaved into the other.

The central aim of Legal Validity is to unravel validity. But one can hardly do this by “pondering over the term” any more than one can “crack the workings of a magic trick by looking up the words ‘hocus pocus’” (p. 3). One must then turn to the point of validity or what validity does – the “technique” of validity. Accordingly, Legal Validity starts off by tackling three puzzles around the point of validity. First, to understand the similarity between uses of validity across the board. Second, to provide an account of how the technique of legal validity is used as a tool to change one's own, and other people's legal relations by saying so – something that is imprecisely described in the literature as a legal power. And third, to lay bare the limitations on power presupposed by the notion of validity.

Chapter 2 of Legal Validity seeks to enquire if validity talk across different domains of law – contracts, rules, passports, IDs, credit cards and so forth – has an underlying similarity, “of which we can eventually probe the moral point” (p. 14). What is common to legally valid results, Köpcke hypothesises, is that they involve a “common and distinct method of changing legal positions…by manifesting one's wish to change them – by saying so” (p. 26). It is the task of Chapter 3 to substantiate this hypothesis. Four aspects of legally valid actions are flagged up for special attention: (1) a valid say-so could result in normative changes beyond what the agent purports to introduce; (2) a valid say-so could “circulate as a relative free-standing entity”; (3) a valid say-so could have unintended consequences; and (4) the validity of a say-so depends upon it following appropriate “requirements and form” (pp. 35–36). The so-called valid contract or valid licence are not “acts” or “physical” things, but rather “placeholders for normative configurations” that have a “built-in reference to the source of the relevant normative configuration” (p. 52). A valid contract, for instance, is an “elliptical” for the verb, or power-exercising act – to contract (p. 54). So much for the legal effects of valid acts. But we also treat legally valid decisions as if they create moral rights and duties.

Chapter 4 seeks to account for how a valid say-so could have such moral power. Unlike some moral duties which arise independently of social arrangements (mala in se), there are others which arise because of them (mala prohibita). In the latter category – into which most legal duties arguably fall – a person acquires a moral duty to do something “in virtue of the fact that many other persons do that same thing” (pp. 70–71). What justifies this technique of specific convergence is that it serves as a means to some aspect of human well-being by lending specificity to some moral requirements, which in its absence would be ineffective, if not downright harmful. Individual conduct becomes morally due and “genuinely apt to serve the moral well-being of others” when it is “part of a larger convergent scheme such as a working traffic order indicating when and where one is to slow and stop” (p. 96).

If the focus of the foregoing chapters was on the ones at the “receiving end”, which is to say, those discharging moral duties generated by the scheme of convergence, Chapter 5 shifts the focus towards those at the “authoring end”, who play a role in creating (marking) and sustaining (enforcing) specific convergence. It explores the ability to create specific moral duties in the first place (p. 96). At the heart of the chapter is the notion of empowerment which is inextricably tied to the idea of “criteria of legal validity” (p. 98). “Criteria of validity are tools for the allocation of legal power, because and through their diverse relationships to the pivotal question of who should decide about what” (p. 101). Consideration of “reasons to empower” help determine “considerations of justice that sound criteria of legal validity” ought to advance (p. 101). “Justice requires that legal power be appropriately allocated” (p. 97). The four considerations of justice are: (1) expertise and capacity; (2) proximity; (3) the Rule of Law; and (4) the value of self-direction (p. 102). These are key to settling issues in a wide variety of areas ranging all the way from freedom of contract to separation of powers.

Legal validity allows a multitude of agents with different spheres of power to speak in one legally salient voice. Chapter 6 argues in favour of the need for law's positivity and seeks to bring out the systemic character of legal meaning presupposed by it. It argues that communities need law's positivity not only to countervail morality's under-determination or controversial character, but rather – and more crucially – law can only be a self-directing undertaking if it is capable of being “shaped in a targeted fashion” (p. 132). Without law's positivity, it would not be possible to change normative relations by manifesting one's intent to do so. What lends coherence among legally valid acts within one legal system is the fact that the agent has less than complete control over the legal meaning of their act. The argument steers a middle way between the communicative model (which equates meaning with communication) and the Dworkinian model of law as integrity which severs the link between the two. Köpcke's picture seeks to hold together the link between authorship and meaning as parts of a fabric of law.

Moving on to Short History, the key revelation of the book is that contemporary preoccupation with validity of legal norms or rules is of recent origin; it is less than 200 years old. For most of history, validity debates revolved around private transactions: contracts, wills, marriages and the like. It is a central aim of the book to home in on not just when, but also why this transformation happens. Short History starts off with Roman law (Chapters 3 and 4). Roman law primarily operates with notions which sound and act like invalidity (rather than validity), such as “irritum” (of no effect), “ruptum” (broken), “non-valet” (not fit for purpose), etc. But these are far from being “juridical terms of art” (p. 27). Besides, Roman law lacks a clear distinction between prohibition and invalidity as we understand it. Rather, one finds the germ of validity elsewhere in the Roman legal landscape – in the twin ideas of: (1) performing a transaction by saying so, the most important form of which was the stipulatio which involved answering a creditor's question by repeating the operative verb (“dari spondes? Spondeo”) (p. 34); and (2) transactions bringing about obligationes, namely the idea that one owes something to another (later defined as “iuris vinculum” by Justinian's Institutes) (p. 35).

In the thirteenth-century Decretals of Pope Gregory IX, discussed in Chapter 6, one sees an ascendant papacy “taking control of its own law by deploying – and thereby developing —the technique of legal validity” (p. 68). More specifically, the idea that things can be officially declared as invalid (“irritum”), as also the increased use of “non-valet” (p. 69). It is here that one also finds the birth of the idea of “invalidum” (Short History, p. 70). Even the abstraction “validitas” makes an appearance here (p. 71).

With some lag, the secular counterpart of this canonical development began to take shape in the law developed by the city-states. The key figure here is of Bartolus, the father of conflict of laws, who relied on the logic of validity to arrive at his conclusions on the subject (Chapter 7). Bartolus discussed the making of valid transactions in terms of “potest” (power) to do so (p. 79). He treated exercises of private power as similar to exercises of public power and envisaged validly made transactions freely circulating across jurisdictions. He also distinguished between the validity of laws and validity of transactions under the law. Faced with the challenge of having to explain the pedigree of laws in the absence of a law maker (as in the case of these city-states), without having to fall back on a purely fictional notion of imperial consent, Bartolus resorted to the logic of empowerment – law made by someone's say-so within the framework of further law. The further law here being the Roman Corpus which the city-states fall back on where there was no clear law.

This idea of law-making being a creature of law, Köpcke reckons, is the harbinger of a “Copernican turn” in legal thought (p. 95). That “Copernican turn” is mediated by the seventeenth-century natural lawyer Suarez (Chapter 8). Here, in Suarez one finds a clear demarcation between invalidity and prohibition which anticipates H.L.A. Hart's nuanced take on the subject in The Concept of Law (Oxford 1961) that is so familiar to us. On Suarez's picture, however, the power to make positive laws is conferred on humanity by God with the limitation that it may be exercised only to make just laws. The maxim long associated with natural law – “an unjust provision cannot be valid (non potest esse valida)” – follows from this (p. 109). Suarez, however, did not have the crucial notion of narrowly “legal” validity.

The narrative then moves on to Savigny and the codification movement in the nineteenth century which is the final link in the chain (Chapter 9). The idea of “declaration of will” is crucial to Savigny's account (p. 120). But, for Savigny, laws, unlike transactions, are not made through declarations of will and he warns against analogising from contracts to legislation. Indeed, it is a part of his project against codification to flag this asymmetry. Savigny's target here was the French Code Civil's equation of the two – that contracts “are binding as laws” (p. 130). But codification does eventually triumph in Germany, as it does elsewhere on the continent. And the key idea underlying codification is that of viewing both transactions and legislation as “products of a technique for crafting general legal changes” (p. 126). The analogy between contracts and legislation so despised by Savigny went on to become received wisdom championed by the likes of Georg Jellineck and got enshrined in the ideal of the Rechtsstaat, which entails understanding state power as arising from itself. The ideal manifests itself in the form of Hans Kelsen's “basic norm”. The basic unit of the legal system came to be a legal norm. Students were taught a “technique for bringing about legal results at scales large and small” (p. 130). The focal point of enquiry came to be flipped. After a long incubation in the private law, the technique of validity was extended to the public law domain. It continues to remain so comfortably ensconced there that it is very easy to forget its beginnings in, or its continuing relevance to, private law and transactions. What this genealogical smidgen also reveals is a shift from viewing regulations on transactions as limitations on an independently held power, to viewing them as regulations conferring power on them. The last of these, it would be obvious, play an important part in Köpcke's own account of legal validity.

In what follows, we will pay closer attention to the idea of legal validity, but before getting there, it might be in order to note something that is conspicuous by its absence in Short History and that is pre-twentieth-century scholarship from the common-law tradition (occasional references to Hobbes, Locke, Bentham and Austin, aside). In all fairness, Köpcke does put in the caveat that “not all landmark texts are studied”; and one can also readily agree that “all studied texts are landmark texts” (Short History, p. 3). All the same, it could be said that whatever value other scholars from the common-law tradition may or may not have added to the project, David Hume would have made for a particularly promising interlocutor, as the following discussion will hopefully go on to show.

As Köpcke rightly notices, practitioners seldom seek to articulate what legal validity is, even though they routinely work their way around its consequences. This is, of course, partly a sobering reminder of the dispensability of theory in the practitioner's life. But could it also be attributed to the fact that what practitioners are bothered about, for the most part, is invalidity rather than validity? Our intuitive response here might be to dismiss this split between validity and invalidity – what is invalid, it might be thought, is just what fails the test of validity. Indeed, in case of a pair of words x and not x, it is usually illuminating to know what the affirmative “x” is, in order to know what the negative “not x” means. However, as J.L. Austin has shown us, there could be cases where one has to know the negative “not x” in order to understand how “x” is used since it is the negative that does all the work. What this translates to is the hypothesis that in some cases, invalidity does the bulk of the work and is key to understanding validity talk. If the hypothesis holds, what the practitioners are more bothered about in such cases is invalidity, which is not captured by the conditions of validity. Take for instance, one of the examples to figure in Legal Validity, namely, that of contracting. Conditions of validity here prescribe what it takes to get into a contract. Contract-invalidating factors – coercion, undue influence, misrepresentation and mistake – are not singled out for special attention by Köpcke (barring the occasional reference to unfair contracts). This should, of course, make no difference if invalidating factors are merely the absence or negation of validity conditions. But as H.L.A. Hart reminds us (“The Ascription of Responsibility and Rights” (1949) 49 Proceedings of the Aristotelian Society 171), this is not the case. The factors that get one out of a contract (invalidity) are not a mere negation or absence of the factors that get one into a contract (validity). The factors that get one out of a contract, form a heterogenous set of non-consent based factors which Hart argues, cannot be captured “in terms of a set of necessary and sufficient conditions”. Now, if the most natural context for validity talk is when invalidity is in question, what may be getting discussed under the rubric of validity talk is factors that get one “out”. In the absence of that context, validity talk runs the risk of sounding incongruous. Consider, for instance, how odd it would be for, say, an art dealer to tell her friend in the course of a conversation that she “validly” sold a painting at work earlier that day. Validity talk only ever begins to make sense here when the invalidity of her sale is in issue (e.g. someone alleges that she misrepresented) and then, it is invalidating factors that take centre stage. If this hypothesis holds, at least in the case of contract, validity viewed as a kind of empowerment would, at best, only be a part of the picture and in order to make sense of validity talk, one would still have to account for the welter of heterogenous invalidating factors that are not capable of being captured in terms of criteria of validity. A little later, we shall try to arrive at rough and ready test for detecting cases where this asymmetry between validity and invalidity is likely to hold.

The foregoing line of thought could be extended further. On Köpcke's account, intentional say-so has a decisive role in transforming the normative situation of parties. To consider the contract example again, in Köpcke's picture it is the act of contracting which transforms the normative situation of parties. Despite influential objections from some quarters, such as Patrick Atiyah, this, no doubt, remains an eminently reasonable position to hold. Yet, a quick survey of invalidating factors in contract law reveals that even though there is little difference qua act of contracting in the form of the agent's epistemic conditions, the normative consequences vary greatly, depending on distinctions about features of the one who induces consent, and the content of what has been consented to (Arudra Burra, “Significance of Consent” (unpublished manuscript)). As Hume notes, qua act of contracting, a dangerously wounded man promising a “competent sum to a surgeon” may not be much different from someone promising a sum to a robber to spare his life (A Treatise of Human Nature (ed. by L.A. Selby-Bigge and P.H. Nidditch) (Oxford 1978), p. 525). However, the normative consequences in the two situations are different. What this goes to show is that invalidity involves considerations which vary from domain to domain; and cannot be fully grasped from the empowerment side of things (or criteria of validity). This overlaps with Hart's insight which was touched upon earlier. It is part of Hume's fascinating account of artificial virtue (which spans across property, promises and allegiance to government) to show how these heterogenous considerations evolve through the shared practice of people and how they relate to validity.

Hume's similarity with Savigny on this point is interesting. As Köpcke notes, for Savigny, what is normatively salient about the performance of a transaction is not an exercise of power, but rather “the set of rules sustained by the shared consciousness of the people” (Short History, p. 123). Little wonder then, that Savigny was bothered with invalidity rather than validity (Short History, p. 122). Hume, however, does recognise the need for the “technique” of “treat[ing] as having normative significance certain publicly accessible and determinate natural facts” (G.J. Postema, Bentham and the Common Law Tradition (Oxford 1982), p. 124, emphasis in original). Hume sees this manifested in the many formal requirements familiar to Roman law and systems of modern law alike, such as the act of promising or the act of symbolic delivery of the keys to a granary. This directly speaks to Köpcke's idea of validity (although Hume does not use the term). Hume's account has artificial virtue – which is cultivated by education and training – at the root of both validity and invalidity. Accordingly, it also accounts for evolution of the heterogenous set of considerations pertaining to invalidity. The crux of Hume's account is that through a process of mutual adjustment and self-correction, participants arrive at a complex set of considerations reflective of public interest and convenience, such as the ones manifested in contract-invalidating factors.

There is another potentially relevant insight that emerges from the foregoing discussion on Hume. In the case of a system which has gradually evolved though practice, as opposed to a deliberately ordered system, there is a greater likelihood of an asymmetry between conditions of validity and invalidity. And that could well be the difference between contracts on the one hand (an institution which has gradually evolved) and passports, IDs and driving licences on the other (ordered systems with rules laid down by an authority at one time). In case of IDs and passports then – unlike contracts – one need not know anything more than criteria of validity to know everything about their invalidity.