The author thanks Peter Benson, Mayo Moran, Sagi Peari, Arthur Ripstein, Ernest J. Weinrib, and the editors and reviewer of the Canadian Journal of Law and Jurisprudence for helpful comments on prior drafts.

1. Emerson, Ralph Waldo, “The American Scholar” in Emerson: Essay and Lectures (New York: Library of America, 1983) 51 at 55.Google Scholar

2. By event I mean such acts as a commission of a tort or a breach of a contract. By condition I mean having something that is rightfully another’s.

3. Birks, Peter, “Equity in the Modern World: An Exercise in Taxonomy” (1996) 26 U.W.A. L. Rev. 1 at 4Google Scholar: “A sound taxonomy, together with a keen sense of its importance, constant suspicion of its possible inaccuracy and vigorous debate on its improvement, is an essential precondition of rationality.” See also Smith, Stephen A., “A Map of the Common Law?” (2004) 40 Can. Bus. L.J. 364 at 365-66Google Scholar: “The academic’s basic goal of understanding the law—or anything else for that matter—is closely linked to the process of mapping. A good map explains what is significant about the data being classified …. [T]he process of mapping, of classification, is inseparable from the process of attaining knowledge.” For a general discussion of the benefits of developing a taxonomy, see McKendrick, Ewan, “Taxonomy: Does it Matter?” in Johnston, David & Zimmerman, Reinhard, eds., Unjustified Enrichment (Cambridge: Cambridge University Press, 2002) 627 at 638 ff.CrossRefGoogle Scholar

4. Waddams, Stephen, Dimensions of Private Law: Categories and Concepts in Anglo-American Legal Reasoning (Cambridge: Cambridge University Press, 2003).CrossRefGoogle Scholar For favorable reviews of Waddams’ work, see Samuel, Geoffrey, “Can the Common Law be Mapped” (2005) 55 U.T.L.J. 271 at 292CrossRefGoogle Scholar: “this monograph will undoubtedly become a, perhaps the, major work on common law reasoning.” See also Hillman, Robert A., “The Many Dimensions of Private Law” (2004) 40 Can. Bus. L.J. 384 at 395Google Scholar: “Dimensions of Private Law is an excellent book. Rich with examples and insights, readers will gain a firmer understanding of the nature of private law and a greater appreciation of its complexity.” For critical reviews, see Smith, “A Map of the Common Law?”, supra note 3 at 366 ff and especially Beever, Allan & Rickett, Charles, “Interpretive Legal Theory and the Academic Lawyer” (2005) 68 Mod. L. Rev. 320.CrossRefGoogle Scholar Steve Hedley responds to Smith, , Beever, , and Rickett, in Hedley, Steve, “The Shock of the Old: Interpretivism in Obligations” in Rickett, Charles & Grantham, Ross, eds., Structure and Justification in Private Law (Portland OR: Hart, 2008) 205.Google Scholar

5. Waddams, supra note 4 at vi and 226.

6. Ibid. at 3. See also Smith, supra note 3 at 367: “Dimensions is unique in this regard: it is the first book-length, inductive critique of mapping.”

7. Waddams, Stephen, “Response” (2004) 40 Can. Bus. L.J. 396 at 398.Google Scholar

8. Hegel, G.W.F., Philosophy of Right, trans. by Knox, T.M. (London: Oxford University Press) at § 33.Google Scholar For an interesting account of Hegel’s conception of classification, see Inwood, Michael “Classification” in A Hegel Dictionary (Oxford: Blackwell, 1992) at 55–58.CrossRefGoogle Scholar For the history of the phrase ‘self-differentiating unity’ in Greek and early Christian philosophy, see Collingwood, R.G, An Essay on Metaphysics (Oxford: Oxford University Press, 2002) at 220.Google Scholar

9. Oakeshott, Michael, “The Concept of a Philosophical Jurisprudence II” (1938) Politica 345 at 352.Google Scholar On the transformative power of a unifying idea, see Emerson, supra note 1 at 69: “ … show me the sublime presence of the highest spiritual cause lurking, as always it does lurk, in these suburbs and extremities of nature; let me see every trifle bristling with the polarity that ranges it instantly on an eternal law; and the shop, the plough, and the ledger, referred to the like cause by which light undulates and poets sing;—and the world lies no longer a dull miscellany and lumber-room, but has form and order; there is no trifle; there is no puzzle; but one design unites and animates the farthest pinnacle and the lowest trench.”

10. Waddams, supra note 4 at vi.

11. Ibid. at 3.

12. Of course, that objections to classification can be mapped does not indicate the features of a successful classification of private law. It merely suggests that criticisms of mapmaking may be self-refuting. Like the relativist who falls on his own sword by denying absolute truth while affirming relativism to be absolutely true, the critic of classification denies the range of classification by offering criticisms that arise within it.

13. Waddams, supra note 4 at 2-3, 226-27.

14. Ibid. at 2.

15. Wittgenstein, Ludwig, Philosophical Investigations, trans. by Anscombe, G.E.M. (Oxford: Basic Blackwell, 1953) at 32e.Google Scholar

16. Waddams, supra note 4 at 191.

17. Ibid. at 19.

18. Ibid. at 34.

19. Ibid. at 14, 22, 222-23.

20. Beever and Rickett, supra note 4 at 331: “Of course, legal maps do not capture the complexity of the law as a whole. They could not perform their mapping function if they did. Just as street maps ignore detail in order to allow a driver to find her way around the area more easily, so legal maps ignore detail—applications of principle to sets of facts, legal procedures, etc.—in order to allow the lawyer to find her way though the maze of legal concepts more effectively.”

21. Waddams, supra note 4 at 3.

22. Ibid. at 226, 232.

23. Ibid. at 142.

24. Ibid. at 190.

25. Ibid. at 183.

26. Ibid. at 226.

25. This account of Aristotle’s answer to the first taxonomical question draws on Weinrib, Ernest J.’s “Corrective Justice in a Nutshell” (2002) 52 U.T.L.J. 349.CrossRefGoogle Scholar

26. Aristotle, Nicomachean Ethics, trans. by Thomson, J.A.K. (New York: Penguin Books, 1976) at 1130b30 Google Scholar: “One kind of particular justice, and of that which is just in the corresponding sense, is that which is shown in the distribution of honour or money … and another kind which rectifies the conditions of a transaction. This latter kind has two parts, because some transactions are voluntary and others involuntary. Voluntary transactions are, e.g., selling, buying, lending, at interest, pledging, lending without interest, depositing, and letting (these are called voluntary because the initial stage of the transaction is voluntary). Involuntary transactions are either secret, such as theft, adultery, poisoning, procuring, enticement of slaves, killing by stealth, and testifying falsely; or violent, e.g. assault, forcible confinement, murder, robbery, maiming, defamation, and public insult.” Note that some editors reject the bracketed text.

27. See Sullivan, Roger, ‘Introduction’ in Kant, Immanuel’s The Metaphysics of Morals (Cambridge: Cambridge University Press 1996) at x Google Scholar: “In the matter of terminology, there are special problems with translating the German word ‘Recht.’ Like the Latin ‘ius,’ it can mean law or justice or right Translated here by the noun ‘right,’ it can refer to the ultimate moral law, or to a system of laws following from it, or to one of the parts of such a system. As an adjective ‘right’ describes behavior that accords with morally correct civil law and that may be coerced legitimately by legal authority. The sense generally is clear from the context.”

28. Kant, Immanuel, Doctrine of Right in The Metaphysics of Morals in Practical Philosophy, trans. by Gregor, Mary (Cambridge: Cambridge University Press, 1996) at 6:230.Google Scholar

29. Ibid.

30. Ibid.

31. Although Kantian right abstracts from the need of agents, its theory of public law recognizes a duty on the state to respect and protect the independence of persons. Persons cannot be independent if their basic human needs are not satisfied. I discuss the duty of the state with respect to the independence of persons in Weinrib, J., “Kant on Citizenship and Universal Independence” (2008) 33 Austl. J. Legal Phil. 1 at 15-25.Google Scholar

32. Pierson v. Post 3 Caines 175, 2 A.D. 264 (N.Y. Sup. Ct., 1805)Google Scholar; Fontainebleau Hotel Corp. v Forty-Five Twenty-Five, Inc. 114 So. 2d 357 (Fla. Dist. CA 1959).Google Scholar

33. Kant, Doctrine of Right, supra note 30 at 6:230.

34. Ibid.

35. Ibid. at 6:237.

36. Schloendoff v. Society of New York Hospital, 211 NY 125 (1914).Google Scholar

37. Kant, Doctrine of Right, supra note 30 at 6:237.

38. Ibid. at 6:237-8.

39. Ibid. at 6:238.

40. Ibid. at 6:237-8.

41. Ibid. at 6:238.

42. Ibid. at 6:231.

43. Ibid.

44. Ibid. at 6:271.

45. Ibid. at 6:247.

46. Ibid. at 6:252.

47. Kant, , The Critique of Pure Reason, trans. by Smith, N.K. (New York: Macmillan, 1985) at A767–8/B795-6 Google Scholar: “JURISTS, when speaking of rights and claims, distinguish in a legal action the question of right (quid juris) from the question of fact (quid facti); and they demand that both be proved. Proof of the former, which has to state the right or the legal claim, they entitle the deduction.”

48. Kant, Doctrine of Right, supra note 30 at 6:248.

49. Ibid. at 6:259.

50. Ibid. at 6:257, 6:264.

51. Ibid. at 6:312.

52. Ibid.

53. Ibid. at 6:306-7. For a discussion of the centrality of this obligation in Kant’s theory of public law, see my “The Juridical Significance of Kant’s ‘Supposed Right to Lie’” (2008) 13 Kantian Rev. 141.CrossRefGoogle Scholar On the obligation to leave the state of nature and enter into a condition of public law, see Ripstein, Arthur, Force and Freedom: Kant’s Legal and Political Philosophy (Cambridge, MA: Harvard University Press, 2009) at 145–81.CrossRefGoogle Scholar

54. Kant, Doctrine of Right, supra note 30 at 6:256.

55. Kant’s account stands in direct contrast with other theorists, such as Locke and—as I will discuss below—Hegel. Locke begins with the second stage and holds that one acquires a right to possess an external thing by using that thing. Whereas Locke holds that one somehow possesses a thing because one has used it, Kant holds that one cannot use a thing unless one possesses it, which in turn presupposes the rightfulness of possession. Turning to the first stage, Locke conceives of property not as a relation between independent persons but rather as a relation between a person and a thing. In this relationship, the person’s interaction with the thing distinguishes the owner from all other persons with respect to it. Kant ridicules this view as a “guardian spirit” theory of property because it suggests that a right to a thing involves a juridical relationship between a person and a thing, in which the owner’s right to the thing is correlative to the thing’s duty to the owner to repel other users. Such a view is inadequate because one’s relation to a thing imposes no juridical duties on others. See Locke, John, The Second Treatise of Government (Toronto, ON: Prentice Hall, 1997) at 16–30 Google Scholar and Kant, Doctrine of Right, supra note 30 at 6:260.

56. Doctrine of Right, supra note 30 at 6:271.

57. Ibid. at 6:281.

58. Kant does not relate his status relationship to fiduciary obligations. Whether the normative structure of a fiduciary obligation is captured by the category of status is a serious question that I cannot consider here. Whereas the category of status considers the right to a person akin to a right to a thing, a further category would arise by considering a right to a thing akin to a right to a person. The incoherence of this possibility precludes its realization in experience. A right to a thing akin to a right to a person would involve a thing imposing a duty on its possessor to refrain from using it. Although persons can impose duties on the activities of others, things cannot impose duties on their possessors to refrain from using them. The freedom of purposive beings may be limited solely by the systematization of that value.

59. Waddams, supra note 4 at 12-13.

60. Ibid.

61. Heraclitus of Ephesus in McKirahan, Richard D. Jr., ed., Philosophy Before Socrates (Indianapolis, IN: Hackett, 1994) at 124 Google Scholar (fragment 10.78 (84a)).

62. M’Alister (or Donoghue) v. Stevenson [1932] AC 562 Google ScholarPubMed (HL) [Donoghue]; Moses v. MacFerlan (1760), 97 E.R. 676 Google ScholarPubMed, 2 Burr. 1005 (K.B.).

63. Donoghue, ibid. at 579.

64. Ibid.

65. Ibid.

66. Ibid. at 580.

67. Ibid.: “You must take reasonable care to avoid acts or omissions which you can reasonably foresee would be likely to injure your neighbour. Who, then, in law is my neighbour? The answer seems to be—persons who are so closely and directly affected by my act that I ought reasonably to have them in contemplation as being so affected when I am directing my mind to the acts or omissions which are called in question.”

68. Supra note 62.

69. Ibid.

70. Seavey, Warren & Scott, Austin, “Restitution” (1938) 54 Law Q. Rev. 29.Google Scholar

71. Ibid. at 31. See also J., Deane in Pavey & Matthews Proprietary Ltd. v. Paul (1986) 162 C.L.R 221 Google Scholar (H.C. Australia): “[The concept of unjust enrichment] constitutes a unifying legal concept which explains why the law recognizes, in a variety of distinct categories of case, an obligation on the part of a defendant to make fair and just restitution for a benefit derived at the expense of a plaintiff and which assists in the determination, by the ordinary processes of legal reasoning, of the question whether the law should in justice, recognize such an obligation in a new or developing category of case ….”

72. Seavey & Scott, supra note 70 at 32.

73. Ibid. at 31.

74. Ibid. at 32.

75. Ibid. at 36.

76. Kant provides a discussion of the role of intermediary principles in public law in “On a Supposed Right to Lie from Philanthropy” in Practical Philosophy, supra note 30 at 8:430. For a discussion of this passage, see my “The Juridical Significance of Kant’s ‘Supposed Right to Lie’,” supra note 53 at 163-64.

77. Seavey & Scott, supra note 70 at 36-37.

78. Omychund v. Barker (1744) 1 Atk 21, 33-4.Google Scholar

79. See Poe et al. v. Ullman, State’s Attorney, 367 U.S. 497 at 542 (1961).Google ScholarPubMed

80. Fibrosa Spolka Akcyjna v. Fairbairn Lawson Combe Barbour Ltd. [1943] AC 32 at 61Google Scholar: “It is clear that any civilized system of law is bound to provide remedies for cases of what has been called unjust enrichment or unjust benefit, that is to prevent a man from retaining the money of or some other benefit derived from another which it is against conscience that he should keep. Such remedies in English law are generically different from remedies in contract or in tort, and are now recognized to fall within a third category of the common law which has been called quasi-contract or restitution.”

81. On the relationship between the Kantian theory of private law and unjust enrichment, see Weinrib, Ernest J., “Correctively Unjust Enrichment” in Chambers, Robert, Mitchell, Charles, & Penner, James, eds., Philosophical Foundations of Unjust Enrichment (Oxford: Oxford University Press, 2009).Google Scholar

82. Kant, Doctrine of Right, supra note 30 at 6:237.

83. Vasan, R.S., ed., The Canadian Law Dictionary (Don Mills, ON: Law and Business Publications, 1980)Google Scholar s.v. “tort” at 381.

84. In his Introduction to the Philosophy of Right, Hegel seeks to distinguish his conception of right from Kant’s, but Hegel’s remarks are either unfortunately opaque or overly uncharitable to his predecessor. Hegel seems to claim that Kant conceives of right as a limitation of freedom rather than an ex Pression of it. For a repudiation of this criticism, see Knowles, Dudley, Hegel and the Philosophy of Right (London: Routledge, 2002) at 54.Google Scholar

85. Hegel, Philosophy of Right, supra note 8 at § 36.

86. Kant, Doctrine of Right, supra note 30 at 6:236. Further similarities could be illustrated with respect to the way in which each philosopher conceives of agency, the free will of agents, and the equality of agents. See Weinrib, Ernest J., “Corrective Justice” (1992) 77 Iowa L. Rev. 403 at 421-23.Google Scholar

87. Hegel, Philosophy of Right, supra note 8 at § 40.

88. For general accounts of Hegel’s theory of private law, see Benson, Peter, “Abstract Right and the Possibility of a Nondistributive Conception of Contract: Hegel and Contemporary Contract Theory” (1989) 10 Cardozo L. Rev. 1077 at 1147 ff.Google Scholar and Brudner, Alan S., “Hegel and the Crisis of Private Law” (1989) 10 Cardozo L. Rev. 949.Google Scholar

89. Kant, Doctrine of Right, supra note 30 at 6:284.

90. My comments on Hegelian classification are drawn from Inwood supra note 8 at 56.

91. Kant, Doctrine of Right, supra note 30 at 6:260.

92. Hegel, Philosophy of Right, supra note 8 at § 40.

93. Benson, Peter, “Philosophy of Property Law” in Coleman, Jules & Shapiro, Scott, eds., The Oxford Handbook of Jurisprudence and Philosophy of Law (Oxford: Oxford University Press, 2002) 752 at 765.Google Scholar

94. Ibid.

95. Ibid. at 766.

96. Ibid. at 766 and 768.

97. Ibid. at 768.

98. Kant, Doctrine of Right, supra note 30 at 6:260.

99. Hegel, Philosophy of Right, supra note 8 at § 36.

100. Ibid. at § 42. Benson, supra note 93 at 805: “Things do not possess legal personality and standing—they cannot have rights or duties and they are not sources of valid claims against others.”

101. Benson, supra note 93 at 770 (my emphasis): “This right to alienate is exclusive in the sense that others are under the correlative disability of no longer having the legal power to make the thing ownerless; they can unilaterally do nothing that restores the thing’s independence, thereby divesting the right-holder of rightful possession.”

102. Hegel, Philosophy of Right, supra note 8 at § 36.

103. Benson, supra note 93 at 770: “The immediate correlative of the right to use is that others are placed under a legal disability: they cannot unilaterally do anything that represents a rightful use of the thing or that causes the first occupant to lose his or her right to use it. And this legal disability can be imposed upon others in general because the act that establishes the property is public in the requisite way.” See also at 777-78: “… given that my mode of appropriating the thing is public vis-à-vis everyone, the one who is placed under the correlative disability counts as anyone in general ….”

104. Hegel, Philosophy of Right, supra note 8 at § 40.

105. Benson, supra note 93 at 766: “The right-disability relation is definitive of first occupancy. The sole question is one of acquisition, that is, whether someone, through his or her unilateral act, has or has not acquired exclusive property in something.”

106. Ernest J. Weinrib, “Corrective Justice,” supra note 86 at 424: “Aristotle’s corrective justice, Kant’s concept of right, and Hegel’s abstract right all refer—though in different terms—to the same bipolar structure of a correlative doing and suffering. Aristotle ex Presses this correlativity as a gain realized by the doer at the expense of the sufferer. Kant and Hegel, on the other hand relate the immediate interaction of doer and sufferer to the juridical structure of right and correlative duty. In natural right theory, the embodiment of the abstract will in one’s body and property creates rights that other agents are under a duty to respect. The duty is owed specifically to the holder of the right, and the violation of that duty entitles the holder of the right to a legal remedy.” See especially Weinrib, Ernest J.’s “Right and Advantage in Private Law” (1989) 10 Cardozo L. Rev. 1283 at 1308.Google Scholar