2.1 Coherence and Consistency in Law

Consistency means absence of contradiction.Footnote ⁹ Propositions are consistent if each can without contradiction be asserted in conjunction with every other proposition in the same set, and with their conjunction.Footnote ¹⁰ Consistency is thus an absolute and logical property: any two propositions either are or are not consistent. By contrast, the conditions of satisfaction of coherence are less precise. The quality of being coherent is often conveyed through mental images and metaphors.Footnote ¹¹ It is often said, for instance, that something is coherent if it hangs together well, if its parts fit and are mutually supportive, if it is intelligible, if it flows from or expresses a unified viewpoint; whereas the same thing would be incoherent if it is unintelligible, fragmented, or disjointed.Footnote ¹² More generally, an attribute of coherence is that the object of enquiry ‘makes sense’, whereas an attribute of incoherence is that it does not.Footnote ¹³

Neil MacCormick once used the following humorous example to make the distinction between consistency and coherence stand out more clearly. MacCormick asks us to imagine a house where the cleaning rules are as follows: leave everything as untidy as possible on Mondays, Wednesdays, and Fridays, but tidy everything up to the highest perfection on Tuesdays, Thursdays, and Saturdays (Sundays are reserved for resting). These rules can be easily observed, in the sense that none infringes upon the other, but they surely give rise to an unreasonable, indeed absurd, way of living, since they do not seem to serve any immediately discernible end – in short, they make no sense. The image of coherence painted by this example, and the general descriptions above, is that of a network – an interdependent web – between propositions and their justification standing or falling together.Footnote ¹⁴

Transposed to law, it is therefore possible to restate the quality of being coherent – that is, a function of the ability to ‘make sense’ – as the degree to which a set of propositions are rationally related to each other and to the ordering values or principles that are thought to justify them – which MacCormick usefully summarised in the pithy phrase ‘axiological compatibility among two or more rules, all being justifiable by reference to some common principle or value’.Footnote ¹⁵

Aiming for axiological compatibility involves a conscious effort to bring two or more propositions into accord with each other. As such, coherence is not an absolute property but rather a matter of degree and interpretation. Whereas consistency ‘is or is not’, coherence can be ‘more or less’. In the same vein, unlike coherence, consistency as a logical property remains agnostic towards the merits of the positions that are made consistent.Footnote ¹⁶ Thus, ironically, greater consistency may actually perpetuate injustice. It follows that between consistency and coherence, consistency is the subordinate and dependent concept. For example, a perceived inconsistency between two judicial decisions may be interpreted away if one goes higher in the level of abstraction and considers the more general norms, principles, or values that have justified them. By the same token, two legal positions that appear consistent because they yield the same outcome may still not cohere if one looks at the norms, principles, or values that have justified them.

2.2 Coherence and Correctness in Law

Unlike coherence and consistency, coherence and correctness in law are generally not conflated with each other at a conceptual level or treated as interchangeable. However, because coherence is not agnostic towards the merits of the propositions that are made coherent, it is sometimes proposed that a requirement associated with coherence is the ability to arrive at right answers. That is to say, it is sometimes proposed that a coherent whole should be able to determine the single correct outcome in particular cases.Footnote ¹⁷ However, this is not precisely the case, and the statement thus requires more nuance so as to avoid introducing distorting expectations of coherence. While there exists correlation between coherence and correctness, it is doubtful that this extends to causation. To see why, we must further distinguish between determinate and demonstrable correctness.

Something is determinately correct when the reasons offered in its support compel it, which is to say when they carry the greatest weight out of all other competing, plausible reasons supporting it.Footnote ¹⁸ Determinate correctness is an instance of so-called ontological objectivity, which seeks to describe the way things are – their nature and existence – in this case by making particular reference to their ability to produce accurate answers.Footnote ¹⁹ By contrast, something is demonstrably correct when its determinate, or at least plausible, correctness can be demonstrated to the satisfaction of everyone, or virtually everyone. Demonstrable correctness is thus an instance of so-called epistemic objectivity, which refers to the state of rational agents having formed a justified belief regarding the correctness of the object in question.Footnote ²⁰ Determinate and demonstrable correctness are not absolute properties, but matters of degree. The stronger the reasons offered in support of an outcome, the more they would determine that outcome and, by extension, the more likely it would be that others are persuaded of the outcome’s correctness.

The above applies to the legal field as well. Law has an arguable character, meaning that statements about its content are in reality arguments supported by reasons whose relative strength and manner of deployment can vary.Footnote ²¹ Evaluating the force of competing legal arguments is bound to be a matter of degree and calls for the exercise of judgement.Footnote ²² Correctness in law, therefore, cannot be simply reduced to a mere pronouncement (e.g. ‘the law demands x’, or ‘party A must bear liability’) but is rather a combination of the content of the pronouncement and the content and structure of the reasons offered in supporting it.Footnote ²³ The quality of correctness in law is always determined and demonstrated relatively to a set of strung-together premises and assumptions acting as reasons favouring some outcomes or courses of action over others.

Because coherence is axiological compatibility with guiding norms, values, or principles, coherence is thus linked to legal correctness in the following manner. One person’s ‘correct’ interpretation or decision may still be thought to cohere better than another’s, given the justification offered for each interpretation or decision, and given the method used to arrive at them. In other words, the existence of a coherent process of reasoning would mean that its outcome has a claim to correctness, but also that such a claim would not be absolute since another person’s process of reasoning may have been performed better, thus making the latter person’s proposed outcome arguably more coherent and with a stronger claim to correctness.

It follows, then, that coherence and correctness in law are not necessarily equivalent properties. An otherwise coherent process of justification may still result in an outcome which we may regard as legally incorrect for being in tension with collective attitudes and beliefs. One may use an appropriate method and link together the various aspects of the legal system in a competent manner (e.g. by properly identifying the relevant materials, legal norms, or past practices) but may nonetheless make a substantive, value-laden interpretation of them, with which at least some participants in the legal system may not agree. By the same token, determining that an outcome is coherent cannot be exclusively a function of the extent to which the decision is considered to be correct in its substance. One may reach a correct decision in substance, which everyone would agree that the law ought to provide, but do so through contradictory reasoning or through a not well-justified process, where the various elements of the legal system have not been linked together adequately or accurately. In such a case, we would be inclined to conclude that coherence is lacking, despite the moral appeal that the outcome itself may have.

2.3 Coherence and Comprehensiveness in Law

Yet a third requirement often associated with coherence is that of comprehensiveness, meaning the absence of gaps or uncertainties and the corresponding ability to readily supply an answer to each and every question that may be raised.Footnote ²⁴ In the legal field, comprehensiveness can be linked to the value of predictability – that is, the ability of the law’s addressees to determine in advance the legal consequences of their actions. Comprehensiveness and predictability are properties that obtain in degrees. Enhancing comprehensiveness, in the sense of expanding the range of readily available answers to distinct questions of law, can result in greater predictability for the legal system’s addressees.

It may be a reasonable assumption to make that if a legal system is sufficiently comprehensive and thus exhibits a high degree of predictability, then it would also be coherent. However, it can be doubted whether such a connection would necessarily exist. Comprehensiveness does seem to improve the chances of overall coherence but probably cannot guarantee it, and, conversely, coherence does seem to improve the chances of eventually experiencing comprehensiveness over time (and hence predictability) but probably cannot guarantee that either.Footnote ²⁵ As was the case with correctness previously, correlation does not equal causation.

The above conclusions follow logically from the previous examination of the links between coherence, consistency, and correctness. Because coherence is characterised by axiological compatibility, as opposed to mere non-contradiction, the predictability that would normally result from a nominally consistent line of interpretations or applications of the law does not mean that these would necessarily exhibit coherence also. Furthermore, one need not be fully comprehensive in scope, or perfectly predictable at the outset, to be coherent. This again applies especially in law, considering the well-recognised need for change and progressive development following the occurrence of novel situations not covered in existing legal instruments or following a change in collective attitudes and beliefs. By the same token, the inverse also holds true. Coherence does not preclude the need at times to strike a different path from what past consistent practice may indicate. Nor does coherence preclude the existence of gaps in the law.

2.4 Summing-up

How do consistency, correctness, and comprehensiveness fare as determinants of coherence? In the abstract, one may be inclined to say that the occurrence of all three is necessary to describe an object of study as coherent in ideal theory. Thus, the perfect co-existence of all three elements will necessarily render the object of study perfectly coherent in an ideal situation. Conversely, the absence of all three elements would render the object incoherent. However, based on the preceding analysis, the same conclusion does not seem to follow in practical, non-ideal situations. Indeed, three general points can be made in this respect.

First, although certainly desirable for coherence to exist, consistency is not a necessary or sufficient requirement of it. The presence or absence of consistency does not necessarily mean that coherence obtains or that coherence is forfeit. In fact, consistency seems to be the dependent concept when seen against coherence. Often, it is a sense of coherence that makes us either disregard contradictions as being only apparent (and thus capable of being interpreted away) or, indeed, call them out as being true.Footnote ²⁶

Second, correctness is likewise not a necessary determinant of coherence. Although there exists a correlation between legal correctness (both determinate and demonstrable) and coherence, this does not extend to causation, given the law’s arguable character and the scope within it for debate and reasonable disagreement. Legal pronouncements may not always be determinately correct, yet they could still exhibit congruence with some of the system’s principles or values and be supported by a competently drafted statement of reasons. Incoherence resulting from a complete disregard of a system’s norms, practices, and principles, or from a complete disregard of the ways of structuring and presenting legal arguments, are likely to be rare.

Third, the same considerations apply also with respect to comprehensiveness as a determinant of coherence. Some unpredictability resulting from an absence of comprehensiveness is not necessarily a sign of incoherence. The law is always a work-in-progress and unpredictable outcomes may be caused by legal actors using novel doctrines, arguments, or theories that are not yet settled or widely accepted in the current state of the discipline.

The above leads to the conclusion that coherence is an independent concept having its own content. Were it not, we could only perceive it to the extent, if any, that it entails or is entailed by consistency, correctness, and comprehensiveness. That is to say, the conclusion ‘coherent or incoherent’ would necessarily follow from any statement about the law, so long as we considered that statement to be consistent, correct, or comprehensive (predictable). However, this does not appear to be the case in practice. To the contrary, we are ultimately not precluded from perceiving coherence in practice or from debating about coherence meaningfully, even when some of the above-identified elements are satisfied to a lesser extent or even entirely missing.

In the same vein, striving for coherence in the determination and interpretation of CIL should not mean that consistency, correctness, or predictability will be necessary outcomes, although they may be probable and, indeed, highly hoped-for outcomes. Does this then make coherence practically irrelevant when engaging in CIL interpretation or, for that matter, in any form of legal reasoning? Section 3 argues that it does not.

3.1 Theoretical versus Practical Reasoning

In theoretical argumentation, one adduces reasons for or against forming a belief about what is or is not the case in reality.Footnote ²⁷ Theoretical reasoning is thus reasoning principally about questions of fact, explanation, and prediction.Footnote ²⁸ As such, it has a backward-looking and a forward-looking dimension. It is backward-looking when it looks at events that have occurred and asks why or how they have occurred. It is forward-looking when it uses past observations and the rules of logic to attempt a true determination about what is going to happen in the future. Given its format and reliance on the rules of logic, theoretical reasoning can be challenged in two ways: first, substantively, when the premises used are not accurate, thus leading to a necessarily inaccurate outcome (inaccurate assessment or collection of data); or, second, formally, when the syllogism itself violates the rules of logical consequence or entailment (impermissible moves between otherwise accurate premises).

Practical reasoning is different. Practical reasoning is reasoning about what to do when faced with a problematic situation. As such, it does not stop at formulating an opinion or belief about what the case may be, as theoretical reasoning does, but continues until one commits to a course of action. Put differently, practical reasoning attaches to a project an actor has (be it a problem requiring solution or a goal to be achieved) and seeks to identify the course of action that would lead to the satisfactory completion of that project.Footnote ²⁹ From this fundamental point, a number of key differences between theoretical and practical reasoning emerge.

First, whereas the ends in a theoretical inference are clearly defined and certain (i.e. ascertaining the truth of a proposition or accepting it as a matter of belief), this is not always the case in a practical inference. Indeed, when we contemplate possible courses of action in practice, we often come across phenomena like complexity, uncertainty, instability, uniqueness, or value-conflict.Footnote ³⁰ In these situations the ends cannot always be taken as given – which is to say, without some prior attempt at ascertaining their desirability or appropriateness as ends to be achieved in the first place.Footnote ³¹ Therefore, in resolving a practical problem, an actor must also deliberate in order to prioritise or reconcile competing ends, including also the requirements underpinning the available courses of action to meet these ends.Footnote ³² Reconciling and prioritising may lead the actor to choose a different course of action and to even amend their original goal. Practical deliberation thus requires the actor to simultaneously determine how to do what seems like a good idea of doing as well as whether it really is a good idea to do it in the first place.Footnote ³³

Second, because ends in practical contexts are not beyond challenge or amendment, rationality in practical reasoning is not based only on logical entailment (as in theoretical reasoning) but also on plausibility. This means that although the outcome of a properly conducted theoretical inference will be the same for everyone, this is not a guarantee in a practical inference.Footnote ³⁴ Two actors may both reason correctly from a logical point of view but still arrive at different courses of action, since there may be multiple suitable ways to achieve the same intended goal. Accordingly, rationality in a practical inference is a function of the degree to which a desirable end x is achieved by a course of action y, subject to any competing or countervailing reasons for not doing y given the possible existence of an additional, also desirable, end z. By enlarging the scope of the debate in this manner, the rationality of a practical inference may be affirmed or challenged.Footnote ³⁵

Third, because of the above characteristics, practical inferences can be challenged in three ways: first, substantively, when the premises used are not accurate; second, formally, when the inference itself violates the rules of logical consequence or entailment; or third, defeasibly, through the introduction of additional contexts to the enquiry that do not necessarily make existing premises inaccurate yet, on balance, render them inappropriate and replaceable by better premises.Footnote ³⁶

3.2 Legal Reasoning as Practical Reasoning

Traditional depictions of legal reasoning in international legal academia have closely tracked the theoretical model of reasoning just described.Footnote ³⁷ Legal reasoning is thus often depicted as a chain of logical deduction consisting of a syllogism of the form ‘if p then q’, where p stands for a proposition of law and q stands for the consequence that follows from it.Footnote ³⁸ The reasoner’s role is to input the set of facts that match the applicable proposition of law in order to get the legally prescribed solution. The more difficult the case, the more complex the chain of reasoning. Although this picture of legal reasoning can be challenged for being outdated and overly formalistic, it remains the prevailing narrative when it comes to CIL. That is, in relation to CIL, the above picture is often reversed by saying that the reasoner’s task is to identify the rule of CIL that is hidden in the raw facts of state practice in a process of logical induction.Footnote ³⁹ Thus, the fundamentally syllogistic ‘if p then q’ format of reasoning is retained.

However, although often presented outwardly as a chain of demonstrable theoretical reasoning, legal reasoning better fits the format of practical reasoning.Footnote ⁴⁰ Indeed, legal reasoning exhibits the three main characteristics of practical reasoning identified previously.

In the first place, legal reasoning intends to lead to action and not simply to the formation of a belief about the way things are in the current state of the law. States typically invoke law and make arguments about the law to justify taking a course of action in the future, to justify having taken a course of action in the past, and to block other states’ justifications for following one course of action rather than another. Similarly, when seised of a case, international adjudicators do not simply declare the law in the abstract; they commit themselves to a course of action by handing down a decision in favour of a disputing party, which is tailored to the particular circumstances of the case presented before them.

In the second place, legal reasoning is a purposive activity. And yet, as the ILC has also affirmed, the law’s ends are not always clearly defined, indisputably certain, or entirely uniform.Footnote ⁴¹ Take international investment law. The preambles of international investment agreements indicate that states enter into them for a variety of reasons, including, for instance, to protect their investors abroad, to stimulate investment flows in their territory, or to contribute to their economic development. The choice to give foreign investors access to investor-state dispute settlement has also been justified on multiple grounds, including as an additional incentive to invest in another countryFootnote ⁴² or as a way to depoliticise investment disputes by removing them from the domain of diplomatic protection.Footnote ⁴³

The same considerations apply, arguably with greater force, in the case of CIL. As Gorobets points out, customary norms are community norms.Footnote ⁴⁴ Therefore, even when it is a small group of states or, indeed, a single state that originally sparked the creation of a CIL norm (one can think of the 1945 Truman proclamation on the continental shelf here), these states may not be regarded as the norm’s authors in exactly the same way as the contracting parties to a treaty are that treaty’s authors.Footnote ⁴⁵ The juridical goals of the original ‘creators’ of a CIL norm are not immune from re-appraisal and re-interpretation by all subsequent actors who may seek to invoke and apply that norm in practice.

The conclusion would not be different even if one were to focus on purely doctrinal goals associated with the law – such as ensuring legal certainty, justice, or the rule of law – and sought to determine how these should be promoted through legal reasoning. We would still need to perform an act of interpretation of these abstract goals case by case, in light of the institutional role of the international actor who advances the legal argument in each instance. In short, interpretability of ends appears to be a ubiquitous feature of legal reasoning.

In the third place, legal reasoning is defeasible. Some legal questions can be genuinely difficult to answer. People who are competent and well informed about the law can still reasonably disagree about its content, despite starting from similar premises and advancing formally valid syllogisms. When lawyers disagree, they do so not only by challenging the accuracy of each other’s chosen premises or the logical consequence of their syllogism, but also by pointing out missing premises or missing contexts in a competing argument, which may render that argument less plausible or convincing.Footnote ⁴⁶

3.3 A Dual Role for Coherence

To recap, legal reasoning is practical in the sense that it seeks to motivate a situated actor, who has certain goals, into committing to a particular course of action. In practical reasoning, an interactive and iterative relationship exists between the actor’s goals, the course of action chosen, and the mental steps taken in between – all these are, moreover, open to deliberation and modification in the course of reasoning. Thus understood, legal reasoning exhibits important coherence-related features. Because it is practical, legal reasoning spans out in a web of clustering reasons for action, rather than extending linearly as a chain. Moreover, by having interpretable goals, legal reasoning relies on axiological compatibility between these goals, the reasons that justify pursuing them, and the appropriateness of the steps taken to achieve them in practice. In other words, like practical reasoning, legal reasoning is meant to lead one to a conclusion about what ought to be done (or not done) given one’s evaluation of a problematic situation to be resolved or a goal to be achieved. The strength of a legal argument thus comes principally from the force of the connection – the degree of mutual supportiveness – between these various clusters of reasons.Footnote ⁴⁷ The latter, in turn, is a function not only of the desirability of the reasons used but also of the way in which these reasons have been structured and made to interact in pursuit of the chosen goal.

What role, then, does coherence play in legal reasoning? I believe it plays a dual role, which is at once substantive and methodological. On the one hand, when faced with a legal problem, one must frame the legal question at issue; identify the normative context, including the governing values, principles, and other norms of conduct, that will guide the decision-making process; and, in so doing, also reflect on one’s institutional role and aims (including on their limits) in the legal system. Coherence here implies an overall congruence with the body of knowledge and value prevalent in the legal system in question,Footnote ⁴⁸ and thus operates in a clearly normative way as a substantive principle. It assists in formulating, even if in the abstract, the end, purpose, or state of affairs to be achieved and the reasons supporting it in principle.

On the other hand, having come up with the end, purpose, or state of affairs to be achieved, one must then proceed by following an iterative process whereby one identifies concrete courses of action to fit the chosen end, purpose, or state of affairs; considers the impact on the identified actions of any countervailing ends, purposes, or states of affairs; in the process potentially reassesses the desirability of the end, purpose, or state of affairs originally chosen; and, if so, reformulates amended courses of action, as appropriate, to fit the reassessed end, purpose, or state of affairs to be achieved. The idea of coherence here takes on a methodological hue. It describes a reflexive process of internal deliberation and a manner of structuring all relevant elements into a justifying narrative that seems at least plausible, if not compelling, to the community at large.

Singled out from the above are three mental processes associated with coherence in law as potential indicators: (1) acts of framing, (2) acts of contextualising, and (3) acts of iteration/reflexivity. Section 4 offers some preliminary thoughts on how these three processes may fit within the interpretation of CIL.

4.1 Framing

Practice is the foundation of CIL’s existence and content: it is practice that becomes law if it is accepted as such by states.Footnote ⁵⁴ Yet, identifying the elements of practice to figure into one’s ascertainment or interpretation of a CIL norm does not proceed on a blank slate. Rather, it presupposes a prior framing of a legal question in need of an answer, or of a problematic situation in need of resolution, forming the contours of a ‘project’ that the interpreter intends to complete as their legal goal.Footnote ⁵⁵ The ‘project’, appropriately framed, helps to kick-start and guide the enquiry methodologically as well as substantively.Footnote ⁵⁶ Thus understood, acts of framing are interpretative in at least three ways.

In the first place, framing helps to formulate legally acceptable goals to be achieved through the ascertainment of the content of a CIL norm. As Hakimi points out, international actors do not approach CIL as detached observers, but rather as ‘advocates advancing their own preferences’.Footnote ⁵⁷ An understanding of the interpreter’s institutional role is therefore important. Different international actors have different institutional roles, affecting the kind of questions that can be asked, the legal problems that need resolving, or the arguments that can be made. For instance, states enjoy greater freedom in devising policy goals to be pursued through legal means. States can thus generate arguments about possible new CIL norms, or about new meanings to be assigned to existing CIL norms, simply by acting and by justifying such action against existing practice or against their reasoned views about the action’s appropriateness or desirability in the legal system.Footnote ⁵⁸ By contrast, the institutional role of international adjudicators is more constrained. When determining the content of a CIL norm, adjudicators can proceed acceptably only by attempting to reconstruct the intentions of those states that have engaged in relevant practice and substantive argumentation in relation to a putative CIL norm.Footnote ⁵⁹

In the second place, framing helps to impose order and priority in the virtual infiniteness of state practice. One cannot hope to isolate those elements of state practice that would be relevant for examination, or to assess their legal relevance, unless one has already framed with some degree of specificity a legal problem to resolve or a legal goal to achieve. If, for instance, one wishes to advocate for a new, less strict content of the CIL minimum standard of treatment of aliens in the context of foreign investment protection, one should look for evidence of such content, among others, in the development of investment treaty provisions over time, interventions made by states before international forums such as UNCITRAL or UNCTAD, positions taken by states in arbitration or in non-disputing state party submissions made in the context of investment disputes, relevant diplomatic exchanges, or even judgments by domestic courts addressing grievances of foreign investors.Footnote ⁶⁰

At the same time, the weight, authority, or priority of different sources of evidence of practice are all relative, meaning that some materials of practice may only be relevant prima facie and that an assessment must be made case by case.Footnote ⁶¹ Thus, in the third place, framing the legal issue appropriately also helps the interpreter to determine the kind of practice they should establish or look for.Footnote ⁶² For example, in Nicaragua v. Honduras, the ICJ considered in obiter that in certain circumstances the application of the CIL principle of uti possidetis could be extended to the delimitation of maritime boundaries (as opposed to being confined to the determination of territorial boundaries), in particular when this is in connection with historic bays and territorial seas.Footnote ⁶³ No new evidence of state practice or opinio juris was offered for this statement, yet arguably none was needed given the framing of the issue. That is, extending the application of uti possidetis from the determination of territorial boundaries to the delimitation of some maritime boundaries may be said to have been a continuation, by analogy, of the ICJ’s prior conclusion, in Frontier Dispute, that uti possidetis is a ‘principle of a general kind which is logically connected with … decolonization wherever it occurs’.Footnote ⁶⁴ Put differently, from the point of view of the juridical aim of securing respect for existing boundaries at the moment of independence,Footnote ⁶⁵ determining a maritime boundary between two newly independent states following decolonisation is not unlike determining a territorial boundary between them.Footnote ⁶⁶

In short, framing kick-starts the interpretative enterprise by singling out what is, prima facie, legally relevant in determining the content of a CIL norm. In doing so, one necessarily ‘bakes in’ certain assumptions, notably about the existing state of the law, about acceptable ends to be pursued, and about one’s institutional role and capacities in the international legal system.Footnote ⁶⁷ Framing thus goes hand in hand with an often-implied process of normative contextualisation.

4.2 Contextualising

Implied in framing is contextualising. The latter involves seeing one’s object of enquiry against an accepted system of background knowledge so as to infer normative content out of it. In the case of CIL, contextualisation takes place when seeking to determine the existence of a CIL norm by carving out an area of relevant practice, and also when seeking to determine the meaning or scope of an already established CIL norm by re-assessing practice that has already been identified in the past. In that sense, like framing, contextualisation in CIL interpretation is indispensable, since mere regularity of conduct cannot lead to a normative conclusion on its own and in the absence of some background context.Footnote ⁶⁸ That is, a collection or a pattern of state conduct cannot by itself be transformed into a reason to act in any particular way absent a rule, goal, or principle acting as the normative context that creates the necessary connections between the observable instances of conduct.Footnote ⁶⁹

Contextualising practice is an interpretative act, in that it can in principle take place at various levels of abstraction. A pattern of conduct may be identified as relevant state practice when seen against broad areas of international law that already include a network of rules, goals, or principles (e.g. use of force, treatment of aliens abroad) as well as against specific international legal rules or doctrines (e.g. uti possidetis, minimum standard of treatment of aliens). Fixing the level of abstraction thus becomes a choice of critical normative importance. The chosen level of abstraction determines not only whether one has identified enough evidence of practice to formulate a CIL norm, but also whether the identified evidence is of the right sort or whether altogether different evidence must be looked for instead.

Take the ICC appeals chamber decision in Al Bashir, which held that there was no CIL rule of head-of-state immunity before international courts (as opposed to before domestic courts) that is applicable in the horizontal relationship between states in situations where the ICC has issued an arrest warrant against a head of state.Footnote ⁷⁰ Put differently, for the appeals chamber, head-of-state immunity would not apply even if the ICC had requested the surrender of a head of state who hailed from a non-state party to the ICC. The ICC appeals chamber concluded so after pointing to the fact that no evidence of practice or opinio juris could be adduced for the existence of a CIL rule of head-of-state immunity in these situations.

For present purposes, one can point out the following vis-à-vis the content-determinative nature of contextualisation. The ICC seems to have initially framed the pertinent legal question adequately (i.e. does head-of-state immunity apply between state parties and non-state parties to an international court when that court has issued an arrest warrant against a head of state?), yet seems to have contextualised its assessment of observable practice narrowly compared to the question (i.e. is there evidence to suggest a rule that states recognise immunity for each other’s heads of state when an international court has issued an arrest warrant?).Footnote ⁷¹ Having done so and having observed no such evidence, the ICC appeals chamber came to the inescapable conclusion that no rule of CIL exists mandating immunity in these situations.

The outcome could have been markedly different had the contextualisation taken place at a higher level of abstraction, for instance by considering the underpinnings of the doctrine of head-of-state immunity. If one takes the view that the doctrine derives from the principle of sovereign equality, then the fact that the immunity may be raised before an international rather than a domestic court becomes immaterial. Instead, what would be critical is whether the head of state whose immunity is waived is a national of a state party to the international court in question. If they are not, the CIL rule on immunity would still apply, since waiving it would violate the principle of sovereign equality.Footnote ⁷² Moreover, making the latter argument does not require one to search for additional evidence of state practice or opinio juris. In fact, it makes the kind of evidence that the appeals chamber was searching for in this instance beside the point.

Crucially, despite the critical interpretative importance of contextualisation, there appear to exist no determining criteria, and no defined metarules, for what the appropriate level of abstraction is in each case a CIL interpreter contextualises practice.Footnote ⁷³ The case rather seems to be that the CIL interpreter, much like other practitioners grappling with doubt or ambiguity in law and elsewhere, must make such determinations on the spot, in the act of interpreting, and without the benefit of hindsight.Footnote ⁷⁴ In the absence of guiding metarules, a conscious and active process of reflection may thus be the only kind of safeguard an interpreter of CIL has.

4.3 Reflexivity

Thinking reflectively consists in ‘turning a subject over in the mind and giving it serious and consecutive consideration’, says John Dewey.Footnote ⁷⁵ According to Dewey, reflective thinking can be a useful method to safeguard one’s inferences from falling into obvious errors.Footnote ⁷⁶ Perhaps the best-known contemporary exposition of reflective thinking comes from John Rawls and his concept of reflective equilibrium as a technique of justification.

Roughly put, the idea behind reflective equilibrium is that we must work back and forth in our reasoning between various levels of abstraction, including between our judgements about particular instances or cases, the principles that we believe underpin those judgements, and the theoretical considerations that we believe bear on accepting our judgements and principles, while revising any of these elements whenever necessary in order to achieve an acceptable level of convergence among them.Footnote ⁷⁷ An acceptable level of convergence, according to Rawls, is ‘wide’ rather than ‘narrow’. That is to say, we should not seek only mere consistency among our judgements, but we should also strive to ensure that some of these judgements provide the best justification for the others. Therefore, it is acceptable for prior judgements to be modified or new judgements to be added during this iterative process.Footnote ⁷⁸ The goal is to achieve an ‘optimal’ equilibrium before stopping the enquiry. We arrive at an optimal equilibrium when the component judgements, principles, and theories of our reasoning are such that we are not inclined to revise any further, because, taken together, they have the highest degree of acceptability or credibility.Footnote ⁷⁹

The reflective equilibrium technique has strong similarities with the understanding of coherence put forward in this chapter as interdependence, mutual supportiveness, and a web of propositions exhibiting axiological compatibility. Not only is interdependence of judgements a core feature of reflective equilibrium, but also the latter’s iterative process precisely seeks to ensure that one’s judgements converge by being mutually supportive and able to stand together as a unit, as the concept of coherence indicates. In short, reflexivity and coherence are conceptually linked. Exhibiting reflexivity in one’s practice is conducive to coherent reasoning, which, in turn, is conducive to a well-justified outcome, substantively as well as methodologically.

A reflexive attitude must thus permeate the entire process of CIL interpretation, permitting and indeed instructing interpreters to critically evaluate and, if need be, amend their interpretative choices and moves before fixing the exact scope of a concrete CIL rule to be applied in the case at hand.Footnote ⁸⁰ No aspect of the process is beyond the possibility of re-assessment and amendment, including, critically, the framing of the legal issue/goal, the chosen level of contextualisation, and the concomitant normative weight assigned to every observable piece of evidence of practice. This makes CIL judgements essentially axiological overall.Footnote ⁸¹ Every interpretative step taken in ascertaining the content of CIL is to be assessed for its conformity to the identified normative background, its consistency with the implications created by earlier argumentative steps, and its practical consequences (whether desirable or problematic) – all combining to yield an appropriate resting place for the interpretative enquiry.Footnote ⁸²

I must make a caveat here. It is not at this point possible to offer a practical example of reflective thinking in CIL interpretation. Much like argumentation in general, putting forward legal arguments or handing down judicial decisions on the content of CIL are performative acts to some extent. That is to say, when expressed publicly, legal argumentation and judicial decision-making are constructed so as to persuade an audience that the argument or decision in question contains well-chosen premises and that the outcome follows rationally from these premises.Footnote ⁸³ There is an inherent difficulty in examining reflective thinking taking place live in practice from that point of view, since any prior act of active reflection during the argument-forming or decision-making process would presently be obscured to the audience.Footnote ⁸⁴ The audience may then only make reasonable retrospective inferences about the reflective thinking likely at play behind the finalised version of the argument or decision presented to them.

Nevertheless, this does not take away from the importance of reflexivity as good practice of an interpreter’s moral responsibility, particularly in light of international law’s arguable character and legal reasoning’s practical nature.