outside the feudal system. Furthermore the co-existence of these estates was common 37 This is different in the area of personal property law, but even there property rights are not completely absolute in the civil law sense. This is caused, in part, by the distinction between common law and equity, but also by the relativity of ownership. What matters is priority of entitlement, not absolute entitlement. 38 See, e.g., what Bridge writes in his Personal Property Law where he defines rights in property and the effect of that relationship on the world at large. Property rights come in various shapesand s We can start by say ing that the question deals with the relationship between an individual and a thing, sizes...There exists also a range of equita ble rights over personalty. The touchstone of a property right is its universality: it can be asserted against the world at large and not, for example, only against another individual such as a contracting partner. This is not to say, however, that universalrights are invincible: common law property rights may in certain instances be overridden, and equitable rights purchaser for value without notice of the legal estate. o assets, are always vulnerable to the bonafide for example the interest of a trust beneficiary in the trus But even though Merrill and Smith come nearer to the civil law understand ing of the numerus clausus doctrine than Hansmann and Kraakman, nevertheless-in essence- their analysis too is that of a common lawyer looking at the civil law. The number of property rights they have found in American property law, also in the light of the duplex ordo of common law and quity, still is so open that what they have found should not be qualified as a numerus clausus but as standard isation Stand ard isation means that a limited number of categories is used for practical reasons, but it does not imply that this number is completely closed Courts may still decide that certain rights, created by two parties and not to be found in the existing categories, bind certain or even all third parties. Standardisation also does not mean that the contents of the various categories is as fixed as it is in the civil law by mandatory rules certainly do not want to argue that the analysis offered by merrill and Smith and by Hansmann and Kraakman is meaningless for a civil lawyer. On the contrary, it makes clear what the functional and economic backgrounds of the numerus clausus doctrine are. It shed light on the ad vantages and disad vantages. the economic benefits and costs of the civil law numerus clausus doctrine. This doctrine, if strictly applied, creates the risk that innovation takes too much time, which might hamper the further development of new categories of property rights that are being developed in legal practice. Two obvious examples are the trust and time-share arrangements. I agree with Merrill and Smith that courts should be extremely careful when they decide to create new property rights. 40 The Dutch experience under the old Civil Code is a good example. The Hoge Raad(Netherlands Supreme Court)in 1929 Lawson and Rudden, Law ofProperty, p. 79 M. Bridge, Personal Property Law(Oxford: Oxford University Press, 2002), pp 28 ff. ridge, Personal Property Law, p. 12. See also Wylie and Kenny, Irish Land Law, pp. 177f (Modern commercial practice has done much in recent decades to break down the concept of absolute ownership of chattels. Indeed, commercial law has adopted many of the concepts originally derived from land law in this respect, so that the leasing and mortgaging of valua ble chattels like ships and aircraft is quite common. 40 I refer to what I wrote a bout a possible introduction of the Treuhand (a trust account under german law) in the Netherlands through case law in my contribution De kwaliteitsrekening als"Treuhand"figuur, in E Dirix and R.D. Vriesendorp, Inzake kwaliteit. De hwaliteits-of derdenrekening naar Belgisch en Nederlands recht(Deventer: Kluwer, 1998), pp 211 ff, esp. pp 226 ffoutside the feudal system. Furthermore, the co-existence of these estates was common.37 This is different in the area of personal property law, but even there property rights are not completely absolute in the civil law sense. This is caused, in part, by the distinction between common law and equity, but also by the ‘relativity of ownership’ . What matters is priority of entitlement, not absolute entitlement.38 See, e.g., what Bridge writes in his Personal Property Law where he defines rights in property: We can start by saying that the question deals with the relationship between an individual and a thing, and the effect of that relationship on the world at large. Property rights come in various shapes and sizes. . . . There exists also a range of equitable rights over personalty. The touchstone of a property right is its universality: it can be asserted against the world at large and not, for example, only against another individual such as a contracting partner. This is not to sa y, however, that universal rights are invincible: common law property rights may in certain instances be overridden, and equitable rights, for example the interest of a trust beneficiary in the trust assets, are always vulnerable to the bona fide purchaserfor value without notice of the legal estate.39 But even though Merrill and Smith come nearer to the civil law understanding of the numerus clausus doctrine than Hansmann and Kraakman, nevertheless - in essence - their analysis too is that of a common lawyer looking at the civil law. The number of property rights they have found in American property law, also in the light of the duplex ordo of common law and equity, still is so open that what they have found should not be qualified as a ‘numerus clausus’, but as ‘standardisation’. Standardisation means that a limited number of categories is used for practical reasons, but it does not imply that this number is completely closed. Courts may still decide that certain rights, created by two parties and not to be found in the existing categories, bind certain or even all third parties. Standardisation also does not mean that the contents of the various categories is as fixed as it is in the civil law by mandatory rules. I certainly do not want to argue that the analysis offered by Merrill and Smith and by Hansmann and Kraakman is meaningless for a civil lawyer. On the contrary, it makes clear what the functional and economic backgrounds of the numerus clausus doctrine are. It sheds light on the advantages and disadvantages, the economic benefits and costs, of the civil law numerus clausus doctrine. This doctrine, if strictly applied, creates the risk that innovation takes too much time, which might hamper the further development of new categories of property rights that are being developed in legal practice. Two obvious examples are the trust and time-share arrangements. I agree with Merrill and Smith that courts should be extremely careful when they decide to create new property rights.40 The Dutch experience under the old Civil Code is a good example. The Hoge Raad (Netherlands Supreme Court) in 1929 37 Lawson and Rudden, Law of Property, p. 79. 38 M. Bridge, Personal Property Law (Oxford: Oxford University Press, 2002), pp. 28 ff. 39 Bridge, Personal Property Law, p. 12. See also Wylie and Kenny, Irish Land Law, pp.177 f. (‘Modern commercial practice has done much in recent decades to break down the concept of absolute ownership of chattels. Indeed, commercial law has adopted many of the concepts originally derived from land law in this respect, so that the leasing and mortgaging of valuable chattels like ships and aircraft is quite common.’) 40 I refer to what I wrote about a possible introduction of the Treuhand (a trust account under German law) in the Netherlands through case law in my contribution ‘De kwaliteitsrekening als “Treuhand”figuur’, in E. Dirix and R.D. Vriesendorp, Inzake kwaliteit. De kwaliteits- of derdenrekening naar Belgisch en Nederlands recht (Deventer: Kluwer, 1998), pp. 211 ff., esp. pp. 226 ff