1 Babylonian Talmud, Baba Mezia, 101a (throughout this chapter the translations are my own). On Rav, see Ephraim E. Urbach, The Halakha: Its Sources and Development (1986), 295–302.
2 Peter Birks, An Introduction to the Law of Restitution (1985), 109–16.
3 Thomas Hobbes, A Dialogue between a Philosopher and a Student of the Common Laws of England, ed. Joseph Cropsey (1971), 55.
4 Especial attention has been paid to German law. See, for example, Thomas Krebs, Restitution at the Crossroads: A Comparative Study (2001); Gerhard Dannemann, “Unjust Enrichment by Transfer: Some Comparative Remarks,” (2001) 79 Texas L. Rev., 1837; B. S. Markesinis, W. Lorenz, and G. Dannemann, The German Law of Obligations, vol. I, The Law of Contracts and Restitution: A Comparative Introduction (1997), 710–816; Reinhard Zimmermann, “Unjustified Enrichment: The Modern Civilian Approach,” (1995) 15 Oxford J. Legal Stud. 403; Reinhard Zimmermann, The Law of Obligations: Roman Foundations of the Civilian Tradition (1990), 834–901.
5 For a brief treatment from an economic perspective contending that Jewish law converges with efficiency, see Aaron Levine, Free Enterprise and Jewish Law: Aspects of Jewish Business Ethics (1980), 78–83.
6 Daniel Visser, “Unjustified Enrichment in Comparative Perspective,” in The Oxford Handbook of Comparative Law, ed. Matthias Reimann and Reinhold Zimmermann (2007), 969, 972–73.
7 Ernest J. Weinrib, The Idea of Private Law (1995), 222–29.
8 Above, chapter 6.
9 Babylonian Talmud, Baba Mezia, 101a.
11 Rashi (Rabbi Solomon Yitzhaki, France, 11th century) on “gilita adaatech deniha lach,” Babylonian Talmud, Baba Mezia 101a; Ramban (Rabbi Moses ben Nahman, Spain, 13th century), Milhamot HaShem on Baba Mezia 101a; Rosh (Rabbi Asher ben Yehiel, Spain, 14th century) on Baba Mezia, chapter 8, 22. This view was described by Rashba, who disagreed with it (see below n. 17), as held by most of the commentators; Rashba (Rabbi Solomon ben Abraham Adret, Spain, 13th century), Hiddushei HaRashba on Baba Mezia 101a. Rabbi Joshua ben Alexander HaKohen Falk (Poland, 16th–17th century), Sefer Meirat Einayim, on Shulhan Aruch 375, n. 7 summed up the view as follows: “Know that according to the opinion of Rashi and the Rosh in several places that ‘he has the upper hand’ means that if the appreciation exceeds the expenditure he takes part of the appreciation like the other planters in the city, and if the expenditure exceeds the appreciation, he takes all the expenditure even though the owner got no benefit from it.” There were many controversies concerning the details of this and similar approaches. What distinguishes these approaches from the minority view mentioned below at 239 is that they involve a comparison of expenditure and appreciation. Encyclopedia Talmudit, v. 23 s.v. “Yored lenichsei haveiro shelo midaato,” chapter 2, gives a catalogue of the various interpretations.
12 Samuel’s formulation of the improver’s remuneration in Babylonian Talmud, Baba Mezia 101a.
13 Falk, Sefer Meirat Einayim, above n. 11, observes about Rav’s award of the upper hand to the improver: “If he had not planted the field, the owner himself would have planted it and expended this amount on it.”
14 Rashi on “yado al hatahtona,” Babylonian Talmud, Baba Mezia 101a.
15 The same rule is mentioned by the Roman jurist Celsus in his treatment of inadvertent improvements; Justinian, Digest, 6.1.38 (Celsus).
16 Alfasi (Rabbi Isaac Alfasi, Morocco, 11th century) Sefer HaHalachot on Baba Mezia 101a; Rabbi Yosef Haviva (Spain, 15th century), Nimukei Yosef, on Alfasi, Sefer HaHalachot on Baba Mezia 101a.
17 Rezah (Rabbi Zerahia Halevi Gerondi, France, 12th century), Hamaor Hagadol, on Alfasi, Sefer HaHalachot on Baba Mezia 101a; Rashba, Hiddushei HaRashba on Baba Mezia 101a; see also Rabbi Yosef Karo (Israel, 16th century), Beit Yosef, Hoshen Mishpat 375, 3.
18 As Rashba puts it, above n. 11, “[on the standard view] the owner gives him what the planters of the city get, meaning, even more than the expenditure; this view is surprising, for on what basis will the owner give the improver more than the latter has benefited him?” Rashba is presumably assuming that the enrichment that the improver can claim consists only in the amount that quantifies his efforts, not in a share of the yield’s appreciation, since the yield belongs to the owner unless he freely parts with it.
19 Rezah, above n. 17.
21 As Ritva (Rabbi Yom Toi ben Abraham Ishvili, Spain, 14th century) explained in glossing Rezah’s idea, “One estimates how much a person would be willing to pay to someone who will undertake to do this as a single project, so that the owners will not have to bother with it by arranging for workmen to come and go; for a person would gladly pay a lot of money for this.” Ritva, Hiddushei HaRitva on Baba Mezia 101a.
22 Regional Municipality of Peel v. Her Majesty the Queen in Right of Canada  98 D.L.R. (4th) 140, 156 (S.C.C.).
23 LAC Minerals v. International Corona Resources Ltd.  61 D.L.R. (4th) 14, 53 (S.C.C., per LaForest J.): “on the assumption that Corona had acquired the Williams property, it would of necessity have had to develop the mine.”