Abstract – This essay considers whether the right at stake in cases of unjust enrichment is consistent with a Kantian conception of right. Although there is support for the view that the right at stake can be traced to the Doctrine of Right, there is divergence over the precise form of Kantian right that the law of unjust enrichment is said to vindicate. The essay examines the validity of the in personam and in rem hypotheses submitted by Ernest Weinrib and Robert Towaka, arguing that Weinrib’s account is incompatible with unjust enrichment theory and that norms of corrective justice cannot respond to Kantian right in private law given that private rights are subsumed by Kant’s conception of public law. A Kantian framework of distributive justice has problems explaining some of the side-constraints on unjust enrichment liability and the right underpinning the doctrine should therefore be located outside of the Kantian edifice.

I – Introduction

I want to ask a philistine question: ‘Why Kant?’ Why the recourse, if recourse it is, to eighteenth-century moral philosophy? Why, in the context of the normative foundations of the law of unjust enrichment, the emphasis on the Doctrine of Right[1]as the basis for theoretical discussion? Does this ‘boring’[2], ‘pedantic’[3] and ‘cryptic’[4] appendix to Kant’s moral thought really hold the key to the ‘mystery’[5] surrounding the origin of the claimant’s right in response to an unjust enrichment? Kant never acknowledged and was ‘presumably unaware of’[6] unjust enrichment as a ground of liability. However, recent legal scholarship attests to the right at stake in unjust enrichment being grounded in the Doctrine of Right. It is thus through an analysis of this scholarship that I will engage with existing Kantian debates against the backdrop of a practical and contemporary area of law. My concern in this essay is not to provide a ‘catch-all’ solution to the aforementioned mystery surrounding the right at stake in unjust enrichment scenarios. Rather, asking ‘Why Kant?’ entails a review of the relationship between unjust enrichment and Kantian philosophy, and whether the right at stake can be seen to tally exclusively with a conception of right outlined in the Doctrine of Right.

The question as to the nature and identification of the right that the law of unjust enrichment is said to vindicate has given rise to competing Kantian hypotheses. This is evidenced none more so by the stark disagreement between Ernest Weinrib and Robert Towaka, both of whom interpret the Doctrine of Right in different ways to advance their own theoretical positions. Weinrib posits that the right that unjust enrichment protects is an in personam right to a ‘causality of the defendant’s will’[7], while Towaka argues, at the other end of the spectrum, that the right in question is an in rem ‘Kantian status right’[8] which is made available to the claimant following the defendant’s violation of a special type of proprietary interest belonging to him/her. These arguments, associated criticisms and relevance to the primary text will be explored below.

My response to the question concerning the extent to which the right underpinning unjust enrichment is grounded in the Doctrine of Right will take into account competing analyses of Kant’s taxonomy of private law. Initially, the divergence over the precise nature of the right at stake in unjust enrichment requires me to look closely at the argument contained within the Doctrine of Right in order to discern whether a) this right is traceable to Kant and b) whether it is in personam or in rem. However, what I also hope to achieve is to show that there is a possible third route of exploration, whereby the right underpinning unjust enrichment may be traceable to Kant, but is neither in personam nor in rem. Instead, this right could be viewed as Kantian in a ‘public’ sense, owing to the fact that Kant’s conception of private right (from which the claimant’s right necessarily sprouts), is merely ‘provisional’.[9] In essence, as is argued by Alan Brudner, Kantian public law ‘[ousts]’[10] private law.

The problem, however, with sticking to the Kantian framework is that it may then be difficult to explain some of the ‘[side-constraints]’[11] on unjust enrichment liability (such as the defendant’s change of position) based on respect for the defendant’s formal free choice. Consequently, in considering the ‘extent’ to which the right underpinning unjust enrichment derives from Kant, my ultimate conclusion will be that this right is not grounded in the Doctrine of Right. This conclusion will be reached in spite of Weinrib’s and Towaka’s protestations, although I will still allocate time to both arguments for purposes of criticism and development of argumentation.

By way of context, my focus for this essay is the common law doctrine of unjust enrichment, and reference will be made at appropriate junctures to English, American and Canadian authorities. Although there has been considerable debate over the precise meaning of ‘unjust enrichment’ – Mark Leeming analysing whether it may be seen as a ‘legal norm in its own right’[12] – such a side-issue is beyond the scope of this essay. My main area of attention will be the core, ‘paradigmatic case’[13] of restitution for mistaken payment.

II – An ‘unnamed principle’[14]

An enquiry into the normative foundations of the law of unjust enrichment is a justified research topic in that it affords the opportunity to question the conceptual structure of Kant’s vision of private law. That the right underpinning, or forming the basis of a claim in unjust enrichment can be said to be located in the Doctrine of Right is a falsifiable hypothesis and worthy of examination. This examination results in implications at both a narrow and wide level. At the narrow level, the examination takes place within the field of unjust enrichment theory through an analysis of the right at stake and the accompanying debates therein. At the wider level, the examination ultimately allows us to look beyond the chosen area and think more deeply about Kant’s overall conception of private law rights. It is in this sense that the unjust enrichment question provides the entry route into a broader discussion of the validity, autonomy and, in the eyes of Alan Brudner, ‘provisionality’[15], of Kant’s vision of private law.

Normatively, a claim in unjust enrichment in English law operates in the following, ‘three-step’[16] way: the defendant must have been enriched; the enrichment must have been made at the claimant’s expense; the enrichment must have been the product of an unjust factor (such as mistake, duress or failure of consideration). All the unjust factors are presented in a 43-strong list compiled by Peter Birks and Robert Chambers in the Restitution Research Resource.[17] Restitution relates to the reversal of an enrichment where it was made as a result of an unjust factor. The enrichment takes the form of either a piece of property or the obtention of some monetary value. The problem faced by legal academics is whether the resulting remedy ought to be personal or proprietary, a problem which is reproduced in the Kantian sphere in respect of the disagreement between Ernest Weinrib and Robert Towaka.

In relation to the question of the nature of the right at stake, Alastair Hudson asserts that the law of restitution ‘creates a new right’[18], rather than giving effect ex post facto to a right that was pre-existing. The ‘new right’ comes into effect upon receipt of the unjust enrichment, depriving the defendant of the ‘value’ (a term whose meaning will also be scrutinised below) received at the expense of the claimant. Hudson neglects to specify the precise nature of right, bar the observation that it is simply ‘new’. Testament to the level of uncertainty in this area, Jennifer Nadler offers a different interpretation, arguing that:

the question of the [claimant’s] right must surely be prior to that of the defendant’s liability, for the [claimant’s] entitlement is what justifies the defendant’s liability, and the conditions of liability must derive from a conception of what the [claimant] is owed.[19]

Given my focus on Kant and the question as to whether the right can be grounded in the Doctrine of Right, I do not want to dwell too much on the debate relating to the point in time at which the right in question comes into effect. Rather, I am merely highlighting it for the purposes of the discussion and as context for what is to follow. Essentially, however, Nadler’s argument is that the right cannot come into effect upon receipt of the unjust enrichment because restitution ought to be understood as ‘giving something back’[20] to the claimant. Nadler goes on to state that without an understanding of the right that the law of unjust enrichment is said to vindicate, there can be no ‘coherent theory’[21] of what makes a particular enrichment ‘unjust’, nor of what unifies the various situations under which ‘enrichments are deemed unjust’.[22]

It is at this juncture in the essay that we can begin to develop an understanding of the lack of a ‘coherent theory’ pertaining to the claimant’s right in response to an unjust enrichment. As it stands, there is a lacuna in common law jurisprudence regarding ‘what the [claimant] is owed and why’.[23] The first American Restatement of Restitution describes the principle underlying unjust enrichment as: ‘a person who has been unjustly enriched at the expense of another is required to make restitution to the other.’[24] The authors of the Restatement, Warren Seavey and Austin Scott, equate the postulate underlying the law of restitution with the postulate of a civil right to compensation for unjustly caused harm.[25] For Seavey and Scott, unjust enrichment conveys the idea that ‘a person has a right to have restored to him a benefit gained at his expense by another, if the retention of the benefit by the other would be unjust’.[26] However, this explanation smacks of circularity and gives no indication of any underlying principle of right underpinning the doctrine. Rather than grounding the postulate in right-terms, the term ‘unjust’ remains vague, and, in the eyes of Jennifer Nadler, acts as ‘a stand-in for some yet unnamed principle’.[27] It is here that we can invoke Kant and the Doctrine of Right to perhaps fill this theoretical void and give substantive content to the ‘unnamed principle’.

III – Kant andWeinrib

Indeed, Ernest Weinrib posits that the normative foundation of unjust enrichment is a claim in corrective justice underpinned by a Kantian conception of right. Specifically, the ‘matter’[28] (object) of the claimant’s right in an unjust enrichment scenario is what Weinrib terms a ‘causality of the defendant’s will’, the form of which is ‘ius personale’[29], or in personam. Kant’s conception of an in personam right is said to ‘[emerge]’[30] from two layers that comprise his classification of rights: innate right and acquired right.

Innate right is the only ‘original right belonging to every human being by virtue of his humanity’[31]. Kant contends that this innate, original right is one’s freedom, namely one’s ‘independence from being constrained by another’s choice, insofar as it can coexist with the freedom of every other in accordance with a universal law’.[32] One’s physical embodiment is a manifestation of this right, although the right comprises several aspects (such as freedom of speech and thought[33]). Together, these aspects constitute what is ‘internally one’s own in one’s relation with others’.[34]

In contrast, acquired rights concern rights to objects which are ‘externally mine’[35] or ‘external to [oneself]’.[36] Given that these objects are ‘distinct’[37] from the person and acquired only through an act of the will, Kant refers to them as ‘external objects of choice’.[38] The acquisition of an ‘external object of choice’ entails a connection with the object in such a way that another’s action in respect of it would count as a ‘wrong’[39] or as an infringement of rights. For Weinrib, an acquired right therefore amounts to a ‘relation between a right-holder and an external object of choice that places others under a duty to the right-holder with respect to that object of choice’.[40] Kant divides acquired right into three kinds of relations that connect a person to an external object of his/her choice. These are classed as rights of ‘substance, causality and community’[41] respectively. Every right that links a person to an external object of choice must fit into one of these categories.

In relation to the essay question, it is to the second category of ‘causality’ that I now turn. Causality concerns the ‘matter’ of a right in personam. Contract right is seen as the ‘paradigmatic’[42] manifestation of a right to a causality. Kant informs the reader that the matter of acquisition in a contract is ‘something external’[43], only to then precise that:

Since it is only the causality of another’s choice with respect to a performance he has promised me, what I acquire directly by a contract is not an external thing but rather his deed, by which that thing is brought under my control so that I make it mine. By a contract I therefore acquire another’s promise (not what he promised) […]; I have become enriched [vermögender] (locupletior) by acquiring an active obligation on […] the means [Vermögen] of the other.[44]

In essence, what the promisee acquires through a contract is the right to the promisor’s performance of a particular ‘deed’, that is, a right to the causality of his/her will. In Weinrib’s eyes, the capacity to determine performance of this deed becomes part of the ‘promisee’s patrimony’.[45] Notably, this right does not arise through the initiative of one sole party as that would contravene the other’s freedom in accordance with universal laws. According to Kant, the contractual right comes into existence through the ‘united choice of two persons’[46]: the promisor’s making of the promise and the promisee’s acceptance of it. The united will establishing the promisee’s contractual right therefore creates an entitlement against a particular person ‘to act upon his causality (his choice) to perform something’.[47] This differs from Kant’s conception of a right to a substance (relational category 1), the ‘matter’ of a right in rem. These rights are good against the whole world because they presuppose a ‘general will’[48] according to which the legitimacy of one’s rightful acquisition is recognised by everybody else and vice versa.[49]

Against the backdrop of this framework, liability for unjust enrichment is said to be an example of the claimant’s ‘in personam right to a causality of the defendant’s will’.[50] The causality in question – the deed whose performance is the matter of the claimant’s right – is framed by Weinrib as the defendant’s ‘retransfer to the [claimant] of the value’.[51] It is at this juncture in proceedings that I can refer back to Alastair Hudson’s quotation in section II. For Hudson, the right that arises in response to an unjust enrichment is ‘new’ because it comes into effect upon receipt of the enrichment and deprives the defendant of the ‘value’ received at the expense of the claimant. I am highlighting this quotation in order to explicate briefly the meaning of the word ‘value’, which is used in a particular way by Weinrib to advance his analysis.

Weinrib construes ‘value’ as the ‘content’[52] of a process of transfer (between two parties) in which ‘something is given for nothing’.[53] When neither party treats the value as the content of a transfer, that is, when the transferor does not intend to transfer the value and when the transferee accepts the value as ‘not having been the content of a transfer’[54], the law corrects this process by requiring restitution of the enrichment. The nature of liability underpinning this process is that the transfer was not intended by either party and is required to be reversed. The fact that the two parties’ wills converge in respect of the ‘non-gratuitousness’[55] of the transfer leads to the creation of the transferor’s right to a retransfer of the value, which, in Kantian terms, amounts to a causality of the transferee’s will.

The right belonging to the transferor is established through the converging unity of the parties’ wills in respect of the non-gratuitousness of the initial transfer. Just as the promisee’s acceptance of a promise made by the promisor established a right to contractual performance, so too does the claimant’s non-gratuitous transfer of the value and the defendant’s acceptance of it as being non-gratuitously given establish the claimant’s right to retransfer. The nature of the liability is such that the claimant has not ‘retained ownership’[56] in the transferred value (as is argued by Robert Towaka), but that s/he has acquired a right grounded in the Doctrine of Right to have the defendant retransfer the value.

If we were to pause at this juncture and revisit the first American Restatement of Restitution (‘a person who has been unjustly enriched at the expense of another is required to make restitution to the other’), the enrichment ‘at the expense of another’ is construed, in Weinribian terminology, as the transfer of value.The ‘unjustness’ denotes the non-gratuitous terms on which the value has been transferred. This dual instance of non-gratuitousness, in Weinrib’s eyes, signifies the Kantian relationship of ‘will to will’[57] that gives rise to the claimant’s in personam right (and, by extension, the defendant’s ‘correlative duty’[58]) to the retransfer of the value. The ‘[requirement] to make restitution’ expounded in the Restatement therefore relates to the performance constituting the object of the in personam right to the causality of the defendant’s will.

IV – Criticisms

Although this account might seem like a convincing endorsement of the claim that the right underpinning unjust enrichment is grounded in Kant’s Doctrine of Right, Weinrib’s analysis raises implications at both a narrow and wide level. At the start of section II, I mentioned that there are implications to consider at both these levels when analysing the ‘extent’ to which the right at stake can be conceived as Kantian. As a reminder, the narrow level relates to the field of unjust enrichment theory and the accompanying debates related to the nature of the right at stake. The wider level concerns Kant’s overall conception of private law and whether its ‘provisional’ character is subsumed by public law. The evaluation at the narrow level – which I will consider first – will lead me on to the evaluation at the wider level in later sections. Ultimately, the Kantian hypothesis fails at both a narrow and wide level, with the basis of the right at stake in unjust enrichment scenarios not grounded in the Doctrine of Right.

Narrowly interpreted, Weinrib’s analysis runs into difficulties. Expressed in Kantian terms, the right at stake in unjust enrichment scenarios is an in personam right to the performance of a particular deed by the defendant, namely the retransfer of the value to the claimant. As seen in section III, the ‘paradigmatic’ manifestation of such a right is the right to contractual performance. Weinrib’s argument therefore hinges upon the idea that the parties’ dealings (the ‘obligation-creating conditions’[59]) in an unjust enrichment setting perform the same role as the principles of offer and acceptance in the law of contract. In relation to the essay question, this hypothesis should be rejected as it results in a claim in unjust enrichment resembling an implied promise to repay, a notion that is ‘suspect’[60] and has ‘long been rejected’[61] in the domain of unjust enrichment theory. Moreover, the hypothesis proceeds on the basis of an erroneous analogy with Kant’s conception of contract right.

The right that the claimant has against the defendant is to a causality of his/her will, which, in a contractual context, relates to the deed whose performance is the content of the promisee’s right, the promisor’s contractual performance. It is the ‘convergence’[62] of the parties’ wills on that performance that creates a contract between the two. As corroborated by Peter Benson, this is reflected in the doctrinal requirement in contract law that an offer must contain all the terms of the contract to be made, with the acceptance assenting specifically to those terms.[63] In an unjust enrichment context, the causality in question is the defendant’s retransfer of the value to the claimant following the former’s acceptance of it as having been transferred non-gratuitously. However, to say, as Weinrib does, that the parties’ wills ‘converge on the [non-gratuitousness] of the transfer of value’[64], is ambiguous as to what the deed ‘must be’.[65] The effect of this ambiguity hints at a missing piece in Weinrib’s jigsaw.

The missing piece in Weinrib’s jigsaw is problematic for unjust enrichment scholars. The missing piece, which is not expressly elaborated by Weinrib, is that the right to performance of a particular deed by the defendant (the retransfer of the value), is predicated on the basis that the claimant transfers the value on the premise that the defendant accepts that s/he will have to transfer it back. As expressed by Matthew Doyle, Weinrib’s rendering results in the parties’ wills converging ‘not on the non-gratuitousness of the transfer of value per se, but on the obligation [my emphasis] to retransfer the value’.[66] The implications of the missing piece are such that it is only in this context – where the defendant has accepted the transfer of the value on the premise that s/he will transfer it back – that the parties can create a right to the retransfer of the value. There is thus a discernible limitation on the expression of the parties’ ‘united will’ in respect of the causality that forms the ‘active obligation on […] the means’[67] of the defendant.

In an unjust enrichment context, such a limitation is ‘fictitious’[68]: transfers of value do not work on the basis that value is given by the claimant and then accepted by the defendant on the premise that it will be transferred back. Otherwise, this would result in a claim in unjust enrichment resembling an implied promise to repay, the problems of which are resumed by Philip Davenport and Christina Harris:

If A pays money to B by mistake, then any obligation B may have to repay that money cannot realistically be said to be based on B’s promise to repay it. This is even more clearly illustrated in cases where B steals A’s money – it is absurd to say that any obligation to repay the money is based on B’s promise to repay […]. The concept of implied promises misses the point of the remedy. The obligation to pay under a restitutionary claim is imposed rather than implied. There is no promise, merely an obligation arising by operation of law from the circumstances in which the benefit was conferred.[69]

Convergence of the parties’ wills on the promise to retransfer the value, rather than on the actual transfer of value itself, is described by Doyle as ‘[loose] and [abstract]’[70], something that Kant would have regarded as ‘insufficient’[71] to create a genuine right to the causality of the defendant’s will. Indeed, the actions of the parties in this context lack the necessary ‘quality of choice’[72] that would allow them to operate as expressions of will in respect of the transfer of the value. In Davenport and Harris’ first example, the paradigmatic case of unjust enrichment, it is not possible to regard A as having transferred the mistaken payment to B on the premise that it would be repaid if, for example, A’s consent was faulty. There is no suggestion that A transferred the money on the premise that it would be repaid. Similarly, if B is unaware that A is making the payment non-gratuitously, it is impossible to regard B as having accepted it on the premise that it would have to be repaid.

At the narrow level of analysis then, the nature of the right underpinning unjust enrichment cannot be grounded in the Doctrine of Right based on Weinrib’s reading of the text. The claimant’s right to performance of a particular deed by the defendant, the retransfer of the value, only comes into effect when the value is transferred to the defendant on the premise that s/he will transfer it back. This tries to equate unjust enrichment with Kant’s exposition of contract formation, the effect of which results in an analysis resembling an implied promise to repay. Typically, these accounts of unjust enrichment have difficulty explaining cases where the defendant has not actively contributed to the chain of events which leads to the conferral of the enrichment.[73]

V – Kant andTowaka

Having allocated time to the in personam case, the analysis of the ‘extent’ to which the right underpinning unjust enrichment is grounded in the Doctrine of Right now invites a discussion of the in rem resolution put forward by Robert Towaka. Towaka’s argument – with its emphasis on corrective justice – provides an entry route into the final analysis at the wider level, namely whether the private rights outlined by Kant are subsumed by his conception of public law. The entry route in question is provided by the idea that it is perhaps distributive norms, rather than corrective, that respond to the demands of Kantian right in private law.

Towaka argues that the claimant’s right to restitution following unjust enrichment is an in rem ‘Kantian status right’ which is granted to the claimant following the defendant’s violation of a special type of proprietary interest belonging to him/her. The special type of proprietary interest is said to take the form of an ‘agenda-setting authority’[74] over the value of the unjust enrichment (‘X’) prior to its disposal to the defendant. The proprietary interest is granted to the claimant by virtue of either:

‘[the claimant’s] ownership of legal and beneficial title over X […] or [the claimant’s] ownership of (a portion of) his own labour X (where receipt of X benefits [the defendant] as a service).[75]

Liability for unjust enrichment results from the defendant’s violation of the claimant’s ‘agenda-setting authority’ over ‘X’. This arises upon the defendant’s receipt of ‘X’ in the absence of ‘non-donative intent’[76] on behalf of the claimant. Towaka argues that this is consistent with Kant’s conception of ‘the wrong in property’[77], namely the ‘[interference]’ with another’s ability to set and pursue such ends as he has set for himself’.[78] For Towaka, the claimant and defendant exist in a ‘Kantian status relationship’[79] which justifies the imposition of a restitutionary duty upon the defendant to act in the claimant’s best interest. The nature of this relationship is derived from Kant’s third category of acquired right, mentioned in section III, namely that of ‘community’. A right to community is described by Kant as a right to another person’s status, ‘insofar as [one gets] a right to make arrangements about him’.[80] These types of ‘status rights’ are said to reflect the claimant and defendant acting in an independent and non-consensual manner.[81]

Towaka’s theory constitutes a corrective justice account of unjust enrichment in that restitutionary liability is conceived as resulting from, and reversing the ‘normative imbalance’[82] which occurs upon the defendant’s violation of the claimant’s right. Under corrective justice, liability for unjust enrichment ensures that the transfer of value accords with the freedom of will belonging to both parties. The restitutionary status right arises upon the conflict between the claimant’s non-donative intent and the defendant’s lack of non-donative intent, which ‘incapacitates’[83] the claimant due to his/her property being in the defendant’s ownership and possession. However, this self-same incapacity is said to justify an award of restitution.

The status right belonging to the claimant, denoting a right to a person ‘akin to a right to a thing’[84], forces the defendant to act in the claimant’s best interest by retransferring to him/her ‘either X value […] or in rem rights to X’.[85] The normative imbalance is reversed in that the claimant is entitled to regain the matter of his/her normative loss, the agenda-setting capacity over ‘X’. This process is resumed by Arthur Ripstein: ‘[r]elations of status are inherently asymmetrical, and so can only be made rightful by restricting the freedom of the [defendant] to act for the purposes of the other person’.[86] Indeed, the ‘asymmetry’ of the relationship generates ‘interdependent’[87] rights and duties which result in the defendant’s conduct being constrained in accordance with universal laws.

It is at this juncture that we can begin to develop an understanding of the wider implications associated with the attempt to ground the right underpinning unjust enrichment in the Doctrine of Right. Although writing from the perspective of property rights accruing upon family and/or relationship breakdown, Matthew Harding offers a critique of corrective justice norms which affects the reception of Towaka’s theory. In relation to unjust enrichment, Harding writes that a norm requiring restitution takes the form of ‘allocation back’[88], which usually implies that the norm in question is ‘corrective’.[89] However, recent academic scholarship in both England and Canada has attested to the allocation of distributive norms being employed in both unjust enrichment and family disputes cases, particularly where the court imputes a ‘common intention’ to the parties.[90]

For Harding, the courts’ imputation of a ‘common intention’ is shorthand for ‘distributive norms specifying grounds for allocation’.[91] The distributive norm, which requires an allocation ‘tout court’[92] based on criteria external to the fact that value passed under a contentious transaction, relates to the parties’ ‘mutual consent to a variation of their rights and obligations’[93] against each other. Harding argues that this emphasis on consent derives its content from Kant’s conception of innate right. In essence, the moral position of a person who consents to a variation of his/her rights is changed in a way that is still consistent with his/her freedom of self-mastery.

The court’s application of a so-called ‘consent-based’[94] distributive norm based on the parties’ common intention helps to frame the ensuing discussion of the general validity and workability of Kant’s vision of private law. Both Towaka and Weinrib argue that norms of corrective justice respond to Kantian right in private law, while Harding argues that distributive norms are equally available to the courts. This disagreement allows us to think about whether any norm of justice can respond to a Kantian right (e.g. that underpinning unjust enrichment) in private law.

VI – Provisionality

Towaka and Harding set the scene for a wider discussion of Kant’s broader vision of law in which his conception of private right – explained through the taxonomy of acquired rights – could be seen to be subsumed by his conception of public law. This may provide the normative content for the idea that certain types of unjust enrichment are liabilities under public law, however, it may also suggest that the nature of the right underpinning unjust enrichment should be located outside of the Kantian edifice. If this is the case – which I argue it is – it would be inappropriate to class the right underpinning unjust enrichment as a form of Kantian ‘public right’. Ultimately, the Doctrine of Right does not provide the normative basis for the right in either a private or public sense.

A close reading of the Doctrine of Right reveals that Kant regarded private rights to external objects as ‘contingent [upon]’[95] a unilateral choice. This point is illustrated through the distinction that Kant makes between innate and acquired rights. As a reminder, innate right requires no positive act of acquisition and pertains to all beings with the free capacity to choose their own ends. Innate right requires no approval from a citizen legislature (the law-making authority referred to in §46) because, as an a priori universal right necessitated by free will, it is already vested with the approval that it needs.

By contrast, the same cannot be said of acquired rights. As noted by Alan Brudner, the distinguishing features of acquired rights are that they ‘require some action by an agent’[96] and are contingent upon an agent’s choice. For example, as seen in section IV, a contractual right to compel another’s performance is conditional upon a synchronised act of offer and acceptance. But, writes Brudner, because ‘no one can impose a binding distribution on others consistently with their innate right of self-mastery, privately acquired rights hold only provisionally’.[97] In essence, privately acquired rights have no ‘conclusive normative status’[98] that a public lawgiver is required to uphold.

In Kant’s state of nature, rights are either knowable a priori and approved by an ‘omnilateral’[99] consent, or they are contingent upon a unilateral choice. The problem, however, is that a unilateral choice cannot consistently bind others in view of the innate right of being one’s ‘own master’[100]. Indeed, as set out by Kant himself, ‘a unilateral will cannot serve as a coercive law for everyone with regard to possession that is external and therefore contingent, since that would infringe upon freedom according to universal laws’.[101] Fundamentally then, rights to external objects acquired in the state of nature lack the ‘imprimatur’[102] of an omnilateral will and are ‘only provisional’.[103]

The ‘provisional’ character ascribed to acquired rights affects their status as valid claims in private law. In essence, provisional rights to external objects acquired in a state of nature lack the ‘actual collective authorisation’[104] of those over whom their proprietary and contractual claims would be binding. In Brudner’s eyes, it follows that under Kantian Right, ‘right is identical with public right’.[105] The implication of this subsumption of private law by public law is that there is no autonomous private right to acquired objects that could be vindicated by corrective justice. At the wider level of analysis, this invalidates the claims made by Weinrib and Towaka that norms of corrective justice respond to Kantian right in private law. Consequently, the nature of the right at stake in unjust enrichment cannot be seen as Kantian in a private sense. Given that Weinrib’s analysis failed at the narrow level, this conclusion is particularly applicable to Robert Towaka.

In relation to the essay question, the idea that private right is ‘displacable’[106] by public right perhaps lends support to the idea that unjust enrichment could be construed as a liability under public law, owing to the fact (as posited by Harding) that it is norms of distributive justice that respond to Kantian right in private law. For Kant, ‘public right’ denotes the ‘sum of the laws’[107] laid down by the united will of all in a civil condition. This comprises both the laws protecting intelligible possession and the laws governing derivative acquisition. The laws governing derivative acquisition through the united will of all constitute ‘distributive justice’[108], for it is the united will of all that determines conclusively what belongs to whom.[109] The implications of this for property are such that rather than being acquired privately, property is ultimately ‘allotted’[110] and ‘[divided]’.[111] Indeed, Kant conceives of a property right not as a relation between a person and a thing, but as a ‘usufructuary entitlement’[112] within a system of common ownership, which is moderated by ‘the sum of all the principles having to do with things being mine or yours’.[113]

In the context of unjust enrichment, the problem with sticking to a Kantian framework of distributive justice is the ensuing difficulty of explaining some of the side-constraints on unjust enrichment liability, such as the defendant’s (possible) change of position. This is exemplified none more so in the balancing exercise between trying to vindicate a claimant’s freedom of choice without violating the defendant’s concurrent right to free agency. The defence of change of position applies where the claimant’s recovery of a mistaken payment would allow him/her to determine how the innocent defendant’s resources should be allocated.[114] A defendant can trigger the defence if, in good faith, s/he spent the money mistakenly paid ‘on a special project that would not have been undertaken but for the discovery of the additional money’.[115]

Allowing the claimant to recover the value of the mistaken payment in these circumstances would protect the claimant’s interest at the expense of the defendant’s anterior claim of respect for free agency. The defendant’s right that his/her free choice be respected is a side-constraint on the court setting aside property rights for the sake of the claimant’s autonomy, meaning that, from a Kantian perspective, justice determined by the united will of all would be antithetical to respect for the defendant’s formal free choice in certain situations.

VII – Conclusion

The answer to the mystery surrounding the nature of the right underpinning unjust enrichment should be located outside of the Kantian edifice. The arguments in favour of a Kantian approach run into difficulties at both a narrow and wide level. The narrow level related to unjust enrichment theory and the way in which Weinrib’s in personam account operated on the basis of an incorrect analogy with Kant’s exposition of contract right, leading to an analysis resembling an implied promise to repay. The analysis at the wider level facilitated an examination of Kant’s vision of private law and its overall subsumption by public law. Norms of corrective justice cannot respond to Kantian right in private law and a Kantian framework of distributive justice has problems explaining the side-constraints on unjust enrichment liability, based on respect for the defendant’s free agency.

Bibliography

Primary Text

Kant, Immanuel, The Metaphysics of Morals, Metaphysical First Principles of the Doctrine of Right, translated by Mary Gregor, (Cambridge: Cambridge University Press, 1991 [1796])

Secondary Texts

Arendt, Hannah, Lectures on Kant’s Political Philosophy, (Brighton: The Harvester Press Limited, 1982)

Beiner, Robert and Booth, William James (eds.), Kant and Political Philosophy: The Contemporary Legacy, (New Haven: Yale University Press, 1982)

Benson, Peter (ed.), The Theory of Contract Law: New Essays, (Cambridge: Cambridge University Press, 2001)

Birks, Peter and Chambers, Robert, Restitution Research Resource, (Oxford: Mansfield, 1997)

Brudner, Alan, ‘Private Law and Kantian Right’, University of Toronto Law Journal, Vol. 61, No. 2 (2011)

Brudner, Alan, The Unity of the Common Law, (New York: Oxford University Press, 2013)

Chambers, Robert, Mitchell, Charles and Penner, James (eds.), Philosophical Foundations of the Law of Unjust Enrichment, (New York: Oxford University Press, 2010)

Davenport, Philip and Harris, Christina, Unjust Enrichment, (Sydney: Federation Press, 1997)

Dixon, Martin, (ed.), Modern Studies in Property Law: Volume V, (Oxford and Portland: Hart Publishing, 2009)

Doyle, Matthew, ‘Corrective Justice and Unjust Enrichment’, University of Toronto Law Journal, Vol. 62, No. 2 (2012)

Gardner, Simon and Davidson, Katharine M., ‘The Future of Stack v Dowden’, Law Quarterly Review, Vol. 127, No. 13 (2011)

Glister, Jamie and Ridge, Pauline (eds.), Fault Lines in Equity, (Oxford and Portland: Hart Publishing, 2012)

Hudson, Alastair, Principles of Equity and Trusts, (Oxford and New York: Routledge, 2016)

Mee, John, ‘Joint Ownership, Subjective Intention and the Common Intention Constructive Trust’, Conveyancer and Property Lawyer, Vol. 71, No. 14 (2007)

Nadler, Jennifer, ‘What Right does Unjust Enrichment Law Protect?’, Oxford Journal of Legal Studies, Vol. 28, No. 2 (2008)

Ripstein, Arthur, Force and Freedom: Kant’s Legal and Political Philosophy (Cambridge: Harvard University Press, 2009)

Seavey, Warren and Scott, Austin, ‘Restitution’, Law Quarterly Review, Vol. 54, No. 29 (1938)

Towaka, Robert, ‘The Status Theory: A Corrective Justice Account of the English Law of Unjust Enrichment’ (2014) <https://search.proquest.com/docview/1650585313?accountid=9730>

Table of Cases

Lipkin Gorman v. Karpnale Ltd [1991] 2 AC 548

Patel v. Mirza [2016] UKSC 42

Westdeutsche Landesbank Girozentrale v. Islington London Borough Council [1996] AC 669

Table of Legislation

American Restatement of Restitution 1937, section 1

[1] Immanuel Kant, The Metaphysics of Morals, Metaphysical First Principles of the Doctrine of Right, translated by Mary Gregor, (Cambridge: Cambridge University Press, 1991 [1796]) (Subsequent references to this text will follow the pagination in Volume 6 of the Prussian Academy edition of this work. These page numbers appear in the margin of Mary Gregor’s translation).

[2] Hannah Arendt, Lectures on Kant’s Political Philosophy, (Brighton: The Harvester Press Limited, 1982) at 7.

[3] Ibid at 8.

[4] Mary Gregor, ‘Kant on Natural Rights’ in Kant and Political Philosophy: The Contemporary Legacy, Edited by Robert Beiner and William James Booth, (New Haven: Yale University Press, 1982) at 64.

[5] Jennifer Nadler, ‘What Right does Unjust Enrichment Law Protect?’, Oxford Journal of Legal Studies, Vol. 28, No. 2 (2008), at 245.

[6] Ernest Weinrib, ‘Correctively Unjust Enrichment’ in Philosophical Foundations of the Law of Unjust Enrichment, Edited by Robert Chambers, Charles Mitchell and James Penner, (New York: Oxford University Press, 2010) at 46.

[7] Ibid at 50.

[8] Robert Towaka, ‘The Status Theory: A Corrective Justice Account of the English Law of Unjust Enrichment’ (2014) < https://search.proquest.com/docview/1650585313?accountid=9730> (accessed 03/01/2017) at 5.

[9] Kant, supra note 1 at 6:264.

[10] Alan Brudner, ‘Private Law and Kantian Right’, University of Toronto Law Journal, Vol. 61, No. 2 (2011), at 297.

[11] Jennifer Nadler, ‘Agency and Autonomy in Unjust Enrichment Law’, in The Unity of the Common Law, Alan Brudner, (New York: Oxford University Press, 2013) at 261.

[12] Mark Leeming, ‘Subrogation, Equity and Unjust Enrichment’, in Fault Lines in Equity, Edited by Jamie Glister and Pauline Ridge, (Oxford and Portland: Hart Publishing, 2012) at 28.

[13] Nadler, supra note 5 at 261.

[14] Ibid at 246.

[15] Brudner, supra note 10 at 295.

[16] Alastair Hudson, Principles of Equity and Trusts, (Oxford and New York: Routledge, 2016) at 537.

[17] See Peter Birks and Robert Chambers, Restitution Research Resource, (Oxford: Mansfield, 1997).

[18] Hudson, supra note 16 at 538.

[19] Nadler, supra note 5 at 246.

[20] Ibid.

[21] Ibid. See also Patel v. Mirza [2016] UKSC 42 at 246, per Lord Sumption.

[22] Nadler, supra note 5 at 246.

[23] Ibid.

[24] American Restatement of Restitution 1937, section 1.

[25] Warren Seavey and Austin Scott, ‘Restitution’, Law Quarterly Review, Vol. 54, No. 29 (1938) at 31-32.

[26] Ibid.

[27] Nadler, supra note 5 at 246.

[28] Kant, supra note 1 at 6:260.

[29] Ibid.

[30] Weinrib, supra note 6 at 48.

[31] Kant, supra note 1 at 6:238.

[32] Ibid.

[33] Ibid.

[34] Weinrib, supra note 6 at 48.

[35] Kant, supra note 1 at 6:249.

[36] Ibid at 6:250.

[37] Ibid at 6:246.

[38] Ibid at 6:247.

[39] Ibid at 6:246.

[40] Weinrib, supra note 6 at 49.

[41] Kant, supra note 1 at 6:247.

[42] Weinrib, supra note 6 at 49. See also Kant, supra note 1 at 6:271-274.

[43] Kant, supra note 1 at 6:274.

[44] Ibid.

[45] Weinrib, supra note 6 at 49.

[46] Kant, supra note 1at 6:271.

[47] Ibid at 6:274.

[48] Kant, supra note 1at 6:259.

[49] Ibid at 6:261.

[50] Weinrib, supra note 6 at 50.

[51] Ibid at 51.

[52] Ibid.

[53] Ibid.

[54] Ibid.

[55] Ibid.

[56] Ibid.

[57] Ibid.

[58] Weinrib, supra note 6 at 51.

[59] Ibid at 52.

[60] Matthew Doyle, ‘Corrective Justice and Unjust Enrichment’, University of Toronto Law Journal, Vol. 62, No. 2 (2012), at 31.

[61] Ibid.

[62] Weinrib, supra note 6 at 47.

[63] See Peter Benson, ‘The Unity of Contract Law’ in The Theory of Contract Law: New Essays, Edited by Peter Benson, (Cambridge: Cambridge University Press, 2001) at 139.

[64] Weinrib, supra note 6 at 42.

[65] Doyle, supra note 60 at 31.

[66] Ibid.

[67] Kant, supra note 1 at 6:274

[68] Doyle, supra note 60 at 32.

[69] Philip Davenport and Christina Harris, Unjust Enrichment, (Sydney: Federation Press, 1997) at 25.

[70] Doyle, supra note 60 at 31.

[71] Ibid.

[72] Ibid.

[73] See Westdeutsche Landesbank Girozentrale v. Islington London Borough Council [1996] AC 669 at 710, per Lord Browne-Wilkinson.

[74] Towaka, supra note 8 at 5.

[75] Ibid at 45.

[76] Ibid at 5.

[77] Ibid at 53.

[78] Arthur Ripstein, Force and Freedom: Kant’s Legal and Political Philosophy (Cambridge: Harvard University Press, 2009) at 76.

[79] Towaka, supra note 8 at 6.

[80] Kant, supra note 1 at 6:260.

[81] See Ripstein, supra note 78 at 21.

[82] Towaka, supra note 8 at 105.

[83] Ibid at 45.

[84] Kant, supra note 1 at 6:359.

[85] Towaka, supra note at 59.

[86] Ripstein, supra note 78 at 79.

[87] Ibid.

[88] Matthew Harding, ‘The Limits of Equity in Disputes over Family Assets’, in Fault Lines in Equity, Edited by Jamie Glister and Pauline Ridge, (Oxford and Portland: Hart Publishing, 2012) at 195.

[89] Ibid.

[90] See, for example, John Mee, ‘Joint Ownership, Subjective Intention and the Common Intention Constructive Trust’, Conveyancer and Property Lawyer, Vol. 71, No. 14 (2007); Nick Piska, ‘Constructive Trusts and Constructing Intention’ in Modern Studies in Property Law: Volume V, Edited by Martin Dixon, (Oxford and Portland: Hart Publishing, 2009) and Simon Gardner and Katharine M. Davidson, ‘The Future of Stack v Dowden’, Law Quarterly Review, Vol. 127, No. 13 (2011).

[91] Harding, supra note 88 at 198.

[92] Ibid at 195.

[93] Ibid at 203.

[94] Ibid.

[95] Brudner, supra note 10 at 289.

[96] Ibid.

[97] Brudner, supra note 10 at 308.

[98] Ibid.

[99] Kant, supra note 1 at 6:259.

[100] Ibid at 6:238.

[101] Ibid at 6:256.

[102] Brudner, supra note 10 at 287.

[103] Kant, supra note 1 at 6:264.

[104] Brudner, supra note 10 at 288.

[105] Ibid at 309.

[106] Ibid at 310.

[107] Kant, supra note 1 at 6:311.

[108] Ibid at 6:306.

[109] Ibid at 6:306-307.

[110] Ibid at 6:312.

[111] Kant, supra note 1 at 6:324.

[112] Brudner, supra note 10 at 293.

[113] Kant, supra note 1 at 6:261.

[114] See Lipkin Gorman v. Karpnale Ltd [1991] 2 AC 548 at 579, per Lord Goff of Chieveley.

[115] Nadler, supra note 11 at 261.