THE APPLICABILITY OF COMPARATIVE CONCEPTS C.J.P. van Laer (Maastricht University)(1) Readers are reminded that this work is protected by copyright. While they are free to use the ideas expressed in it, they may not copy, distribute or publish the work or part of it, in any form, printed, electronic or otherwise, except for reasonable quoting, clearly indicating the source. Readers are permitted to make copies, electronically or printed, for personal and classroom use. Contents 1. Introduction 1.1 Comparative concepts 1.2 The applicability of comparative concepts 2. The formation of comparative concepts 2.1 Extensional concepts 2.2 Functional concepts 2.3 Immanent concepts 3. Comparative concepts of empirical use 3.1 Extensional concepts 3.2 Functional concepts 3.3 Immanent concepts 4. Comparative concepts on the Internet 4.1 The Index to Foreign Legal Periodicals 4.2 Comparative thesauruses? 5. Conclusions References Footnotes 1. Introduction 1.1 Comparative concepts It is still an open question posed to the discipline of comparative law how to develop a satisfactory set of concepts to be used for stating and thinking about particular problems or hypotheses. To this question, I have elaborated some answers in my doctoral dissertation (Van Laer, 1997; in Dutch). The book has an English summary, which is also available on the Internet (http://www-edocs.unimaas.nl/general/ism1997.htm#CvL). The English summary gives an idea of two subjects, comparative systems of arrangement and characterization in private international law. These subjects are discussed in the book, not in this article. This article is intended to shed light on the arguments given in the other chapters of the book.(2) The core issue of this article is the suitability of comparative concepts for comparative legal studies. The question of whether such comparative concepts are of any use has not been answered conclusively. In this article, I have attempted to synthesize some important points from of the literature. But first, some introductory remarks will be made in order to offer a framework. Comparative concepts belong to the conceptual apparatus with which the comparatist can approach his discipline, a field which is not limited to only one legal system. Specifically, comparative concepts are concepts that are applied in micro-comparative research, i.e. research carried out at the level of parts of legal systems. Correspondingly, comparative concepts are inadequate for dealing with legal families or with legal systems in their entirety. The proposition of this article is that comparative concepts enable us to compare legal rules belonging to different legal systems. Examples of comparative concepts are 'adoption' and 'unjust enrichment', which refer to legal rules within different systems. The premise of this article is that comparative concepts are criteria on the basis of which the rules of different legal systems may be compared. The legal rules to be compared must have the 'intension' of the comparative concept. This condition can be explained as follows: the intension includes the characteristics determining the applicability of the concept. The intension of the comparative concept is important since the intension must be explicit in order to make understandable which characteristics of legal rules account for their comparability. 1.2 The applicability of comparative concepts As stated above, comparative concepts are criteria on the basis of which the rules of different legal systems may be compared. This premise needs some further explanation. Clusters of features are associated with terms like 'adoption' and 'unjust enrichment'. The comparatist will have to know which legal rules are the referents of these terms. The criteria of comparative concepts must be observable criteria enabling us to investigate empirically the rules belonging to different legal systems. However, the researcher preparing his investigation cannot be sure that the chosen concept includes observable criteria for its application. Results from other comparatists, if available, are not always sufficient to justify this conclusion. Therefore, in the first phase of comparative research, it is wise to assume only that legal rules are comparable. Comparative concepts do not stand for innate notions which are present in the human mind, but for observable criteria. The first phase of comparative research is of primary importance since observable criteria may prevent a waste of time in a later phase. The comparatist wants to study real referents of the comparative concept he has chosen as his starting point. Consequently, a hypothesis must be tested on the legal systems compared. I call a hypothesis containing a comparative concept the 'comparability assumption'. An example of such a comparability assumption is the following statement: because of the comparative concept of 'adoption', the Dutch rules for 'full adoption' can be compared to the Austrian rules governing 'limited adoption'. Such sentences do not give immediate practical advice; they say something about the legal rules of different systems. If the comparability hypothesis is verified, the Dutch rules are really comparable to the Austrian rules. A comparability assumption which cannot be falsified does not contain observable criteria. To find observable criteria for the comparability assumption, the researcher can begin by analysing legislative definitions in order to determine the respect in which he can compare different legal systems. The following definitions of the Dutch 'appartementsrecht' and of the German 'Wohnungseigentum' will illustrate this seemingly simple preparation of comparative studies. The Dutch 'appartementsrecht' is defined as follows: 'An apartment right means a share in the property which is involved in the division and includes the right to the exclusive use of certain portions of the building which, as indicated by their layout, are intended to be used as separate units'.(3) Section 1 of the German Condominium Act defines 'Wohnungseigentum' differently: 'Residential property is the separate ownership of an apartment in connection with the co-ownership share of the joint property, to which it belongs'.(4) Since 'the right to the exclusive use' is mentioned only by the Dutch legislator, this characteristic does not offer a common perspective which could be chosen as a starting point. By contrast, the legislative definitions allow the researcher to compare in the uniform perspective of 'co-ownership'. The comparative concept of 'co-ownership' is the unequivocal intension which may be part of a comparability assumption. If this hypothesis is verified, it is possible to make a real distinction of differences and similarities between the Dutch 'appartementsrecht' and the German 'Wohnungseigentum'. Concomitantly, I do not consider equivocal intensions to be observable criteria since concepts which prove to have different meanings cause the misinterpretation of research results. These comparative concepts are without empirical use for the reason that they amount to mixing up differences and similarities. By definition, comparative concepts that are not applicable in comparative studies, are not applicable either in areas in which comparative law functions as an aid. Correspondingly, I make a distinction between the direct and indirect applicability of comparative concepts: their usefulness in comparative law (direct) and their usefulness in areas of application outside comparative studies (indirect). In sections 2 and 3 the conditions under which comparative concepts are directly useful are discussed; in section 2 three different forms of comparative concepts are dealt with and section 3 examines their relative usefulness in comparative law. Section 4 discusses the Internet as an area of practical application in which comparative law merely serves as an aid. 2. The formation of comparative concepts 2.1 Extensional concepts This section contains a brief analysis of three forms of comparative concepts: extensional concepts, functional concepts and immanent concepts. These forms have to be distinguished before examining their relative usefulness in comparative law, the subject of section 3. First, the formation of extensional concepts will be made clear. The formation of extensional concepts is the listing of common elements which may be present in several legal systems. These common elements are to be found at the intersection of different sets of legal rules, or parts of rules, belonging to different systems. In this view, the national sets of rules could be identified by means of legal terms, e.g. the Dutch 'appartementsrecht', the German 'Wohnungseigentum' and the French 'copropriété des immeubles batis'. Without choosing any intension for the comparative concept, the extensional concept of 'apartment ownership' refers to the common elements at the intersection. The following example will illustrate the formation of extensional concepts. The comparatist may juxtapose the following rules of German 'Diebstahl' and of English 'theft', respectively: 'Whoever takes moveable property not his own from another with the intention of unlawfully appropriating it to himself shall be punished ...',(5) and: 'A person is guilty of theft if he dishonestly appropriates property belonging to another with the intention of permanently depriving the other of it.' The first rule has been identified by the German legal term 'Diebstahl' and the second one by the term 'theft' in the English Theft Acts. Further, the common elements have to be found at the intersection of these rules. The comparatist may decide that 'property' and 'appropriation' are common elements, intuitively excluding 'unlawfully' and 'dishonestly'. He may conclude that the German 'Diebstahl' and the English 'theft' are comparable since extensional concepts result from the listing of common elements. 2.2 Functional concepts The formation of functional concepts occurs in relation to social problems to which legal rules are a solution. In this view, the starting point for comparison is not to be found in law itself but in social problems. For instance, different rules of 'full adoption' and of 'limited adoption' will be regarded as a means of solving the problems of neglected children. Functional concepts arise from the perspective of social science. This perspective is external to the legal systems under comparison. Correspondingly, the complete abstraction from national concepts must be achieved. Functional concepts are expected to refer to legal rules although functional concepts should be completely independent of legal concepts. Functional concepts are related to factual needs or problems of different societies. In this view, the legal rules of different systems would produce social effects on human behaviour which, in its turn, is expected to meet the needs of societies. Correspondingly, the comparatist has to identify common needs or common problems and he has to determine which legal rules are solutions to these common problems. Legal rules considered to be solutions justify the formation of the functional concept. These premises underlying the functional approach lead to the starting point for comparison: the functional concept, e.g. 'apartment ownership', permits the comparison of rules of different legal systems in respect of similar needs or problems such as housing shortage. 2.3 Immanent concepts The formation of immanent concepts occurs as a result of simplifying national legal concepts. Immanent concepts are only criteria for the common characteristics shared by the national concepts being compared. An example of an immanent concept is 'adoption', a concept which exclusively contains the shared characteristics of 'full' and 'limited' adoption. Immanent concepts are criteria for common characteristics by abstracting from national characteristics which do not have counterparts in the other legal system under investigation. Specific sanctions connected to violations of legal rules are examples of such national characteristics. It should be pointed out here that immanent concepts are non-functional concepts. The formation of immanent concepts does not require complete abstraction from national concepts. In this view, the starting point for comparison should be found in law itself, not in social problems. Immanent concepts are neither functional concepts nor extensional concepts. As regards the second distinction, the formation of immanent concepts is not the listing of common elements to be found at the intersection of different sets of legal rules. Immanent concepts do not result from common elements but from criteria commonly used by national concepts. The sameness of intension of immanent concepts entails the comparability of legal rules belonging to different systems. 3. Comparative concepts of empirical use 3.1 Extensional concepts This section contains an assessment of the usefulness of the three different forms of comparative concepts: extensional concepts, functional concepts and immanent concepts. The relative usefulness of these forms depends on their possibilities for empirical use in comparative law. As remarked in subsection 1.2, the criteria for comparative concepts must be observable and unequivocal, enabling us to investigate empirically the rules belonging to different legal systems. The comparatist must test the comparability assumption on the legal systems compared since he wants to study real referents of the comparative concept he has chosen as his starting point. These conditions are important to assess the suitability of comparative concepts for direct use. First, the question of whether extensional concepts are of any use will be answered. There is a controversy between the well-known comparatists Constantinesco and Kokkini, which helps to assess the relative usefulness of extensional concepts. The common comparative denominator which Constantinesco proposes is nothing more than an extensional concept. He states that common elements are present within several legal systems to provide a common comparative denominator. In his opinion one can start to compare as many legal rules as one desires since sufficient relationships govern the selected rules of different legal systems. He goes further when he asserts that the legal rules to be compared provide their own comparability, at least in the initial phase of comparative research.(6) According to Constantinesco, comparative concepts are useless in the initial phase of research. Contrary to the views expressed by Constantinesco, Kokkini postulates the suitability of comparative concepts for direct use in the initial phase of comparative research.(7) Comparative concepts are important since they prevent a waste of time in a later phase of research. Testing the comparability assumption must take place as soon as possible to exclude disappointments after visiting many libraries in different countries in order to study information which proves to be irrelevant because of the absence of comparability. According to Kokkini, comparative concepts serve as unequivocal starting points, which must be upheld in later phases of comparison. The controversy between Constantinesco and Kokkini does not decisively assess the relative usefulness of extensional concepts since Kokkini does not explicitly reject the empirical use of extensional concepts. Therefore, I have developed the following arguments against extensional concepts: national terms cannot identify the common elements of, e.g., 'apartment ownership'. The intersection containing the common elements can only be identified if the common characteristics of these rules are known. Rules are at the intersection of different legal systems if and only if they have the characteristics included in the common intension of the comparative concept. As will be shown, extensional concepts do not comply with the conditions explained in subsections 1.1 and 1.2, stating that the intension of the comparative concept must be explicit and unequivocal. The juxtaposition of legal rules, e.g. those of the German 'Diebstahl' and of the English 'theft' mentioned in subsection 2.1 above, is not sufficient to conclude that common elements are present. After all, the national terms 'Diebstahl' and 'theft' only refer to German and English rules, respectively, without relating these rules. A listing of national terms does not determine the intension to establish that 'property' and 'appropriation' are two similarities justifying the comparability of the German 'Diebstahl' and the English 'theft'. The terms 'unlawfully' and 'dishonestly' could also belong to the common elements. The comparatist cannot objectively exclude these elements as being purely national elements without using the criteria that goods must be moveable and that it must be possible for another person to own them. The comparatist needs a uniform perspective like that of 'co-ownership' in the context of 'apartment ownership' described in subsection 1.2. Terminological resemblance does not guarantee any conceptual correspondence fixing the comparability of the rules of different legal systems. Extensional concepts do not necessarily provide observable criteria that enable us to investigate empirically the rules belonging to different legal systems. Extensional concepts do not justify the comparability of legal rules. They do not make understandable which characteristics of foreign legal rules account for their comparability. The legal rules to be compared do not provide their own comparability. Comparability is not a given fact which is without doubt. Therefore, it has to be discussed which concepts are useful to compare legal rules: functional concepts on the one hand, or immanent concepts on the other. 3.2 Functional concepts The controversy between Zweigert/K?tz and Constantinesco helps to settle the relative usefulness of extensional concepts since Zweigert and K?tz strongly subscribe to the applicability of functional concepts, whereas Constantinesco rejects their functional approach. According to Zweigert and K?tz,(8) a social function is the common perspective the researcher needs. They state that rules of different legal systems can be compared if they serve the same function. In their view, the legal rules of every society essentially face the same problems. As Zweigert and K?tz are sceptical of the conceptual constructs of particular nations, complete abstraction from national concepts is to be achieved with the help of functional concepts. Conceptual systems would only generate some order in national law. Thus instead of asking, 'What formal requirements are there for sales contracts in foreign law?', they prefer to ask 'How does foreign law protect parties from surprise?'. Constantinesco rejects the standpoint held by Zweigert and K?tz.(9) His criticism can be illustrated by focusing on the phrasing 'How does foreign law protect parties from surprise?' In this exemplary phrasing, Zweigert and K?tz omit the legal concepts of 'formal requirements' and of 'sales contracts' in the initial phase of comparative research. According to Constantinesco, they do not make a distinction between the various legal problems which have been specified by national rules. His criticism can be summarized in the following way: as concepts for describing legal rules, Zweigert and K?tz's functional concepts are too broad and ill-defined. However, Zweigert and K?tz do not answer Constantinesco's criticism. No discussion between these scholars has been found in the literature. The following arguments may complete the criticism by Constantinesco: in order to test the comparability assumption containing the functional concept, the causal relation between legal rules and the resolution of a social problem needs to be established. The social effect of legal rules is difficult to determine, however, so in most cases Zweigert and K?tz's functional concepts have no empirical use. A further explanation will be given to clarify these additional arguments. The formation of functional concepts occurs in relation to social problems such as housing shortage, to which, for instance, the rules of 'apartment ownership' are solutions assuming that the legislator cares about the building of apartments. Consequently, the comparatist has to investigate the societal impact of different sets of rules of 'apartment ownership'. Specifically, he has to investigate every desirable or undesirable effect of the legal rules of 'apartment ownership'. Such rules may promote the conforming behaviour of investors in one society, but may not have the same positive consequences in a different society because of impediments to the law's effective functioning. Illustrating one of the most important impediments, some ignorance of the law may intervene between the promulgation of the law and the behaviour of potential investors. The rate of conforming behaviour may vary greatly in the societies under investigation; this circumstance turns the formation of functional concepts into an almost arbitrary decision. Besides, the comparatist is not limited to those rules legally defined as rules of 'apartment ownership' since, according to Zweigert and K?tz, the starting point of comparison should not be found in law itself. If different rules may solve the social problem of housing shortage, the comparatist has to expand his research to functional equivalents such as building regulations. Comparative investigation of the effects of legislative attempts to use law to solve a social problem requires research in various societies. This complex research must show complete conformity to the rules of law in order to establish that different legal systems can be compared since they serve the same function. As intimated earlier, the social consequences of legal rules are difficult to determine. Zweigert and K?tz's functional concepts have their drawbacks since their functional approach rests upon several simplifying assumptions concerning the relationship between needs or problems of different societies on the one hand, and rules of different legal systems on the other. 3.3 Immanent concepts First, a distinction has to be made between Drobnig and Eltzbacher's opinions since Eltzbacher is more straightforward than Drobnig. However, modern literature has paid no serious attention to Eltzbacher's views. An explanation may be that the functional approach is the dominant trend in modern comparative law. Explaining why Drobnig has to be considered a representative of the functional approach will help to assess the relative usefulness of purely immanent concepts. The end of this subsection refers to Constantinesco's criticism, which may help the reader to draw the conclusion that immanent concepts are to be preferred to Zweigert and K?tz's functional concepts. Drobnig takes a middle position.(10) On the one hand, he subscribes to a sociological nature of his comparative concept, on the other hand he selects 'typical solutions' as utilized within a representative legal system, e.g. the solutions offered by the English 'trust'. According to Drobnig, 'typical solutions' are comparative concepts which are useful in presenting the outcome of an investigation, for instance, in the International Encyclopedia of Comparative Law. These 'typical solutions' offer precise descriptions of legal rules since they are not cut loose from their conceptual contexts. So far, the 'typical solutions' must be considered to be immanent concepts embedded in their legal systems. However, being based on sociological concepts Drobnig's comparative concepts are equivocal because they amount to mixing up functional concepts and immanent concepts. The real comparability of the described rules is an open question. Eltzbacher's immanent concepts are purely non-functional concepts without reference to social problems. Eltzbacher does not require the complete abstraction from national concepts. He prefers to look for common characteristics by abstracting from those national characteristics which do not have counterparts in the other legal system under investigation.(11) Preferring this partial abstraction, Eltzbacher bases the formation of immanent concepts on common features within the legal regulation of different legal systems. However, he treats the formation of immanent concepts without considering the important testing of the comparability assumption as pointed out in subsection 1.2 above. In spite of that, I will plead in favour of the empirical use of immanent concepts although the formation of these concepts is difficult. As remarked in subsection 2.3, immanent concepts are criteria for common characteristics shared by the national concepts being compared. Preparing an empirical investigation concerning 'adoption', the French researcher, for example, has to recognize the distinction between the national concepts 'adoption plénière' and 'adoption simple' in order to determine the respect in which he wants to compare different legal systems. This distinction must be made since the comparative concept of full adoption does not refer to foreign legal rules corresponding to the French 'adoption simple' or limited adoption. Juxtaposing articles 356 and 364 of the French Civil Code may help the comparatist to find the intension for this distinction: 'Adoption confers on the child a filiation which substitutes for its original filiation; the adopted child ceases to belong to its family of blood, ...'; and: 'An adopted child remains in his family of origin and conserves all its rights therein, ...'.(12) The first sentence refers to the effects of full adoption, the second one concerns limited adoption. Different legal effects establish the distinction between full adoption and limited adoption within the French system. These national concepts have different intensions. Choosing the intension of full adoption, the researcher will exclude those forms of adoption which do not terminate all legal ties between the child and his biological family. The two intensions of full and of limited adoption are immanent concepts applicable to foreign rules. Further, the comparability assumption has to be tested since specific effects connected to legal rules could be national characteristics without counterparts in the other legal system under investigation. The absence of legislative definitions makes it difficult to choose an immanent concept in order to determine the respect in which the researcher can compare different legal systems. In a case of absence of these definitions, the formation of immanent concepts depends on the structure of the conceptual systems in which these concepts have been embedded. If these systems show almost the same structures, there is an indication that immanent concepts can be found. However, immanent concepts are of no empirical use if the hierarchies of legal systems are too divergent conceptually. Comparing the positions of concepts within their respective hierarchies is important to determine the relationship of these concepts but similar positions do not guarantee any conceptual correspondence fixing the comparability of the rules of different legal systems. A common characteristic cannot be found if branches of law do not show sufficient correspondence at higher and lower levels. E.g. 'real property' in English law and 'biens immeubles' in French law are branches of law missing a common characteristic at a higher, more general, level: while 'real property' looks to procedure, 'biens immeubles' looks to substance.(13) This fact impedes the comparatist in his search for a shared characteristic at a lower, more specific, level in the conceptual hierarchies of the respective legal systems. A common characteristic cannot be found for the English concept of 'chattel mortgage' on the one hand, and the French concept of 'hypothèque mobilière' on the other. The researcher is confronted with a gap when looking for a conceptual equivalent since the English 'chattel mortgage' and the French 'hypothèque mobilière' belong to different branches of law. The lack of a common characteristic at a higher, more general, level makes the structure of the conceptual systems being compared too divergent. This fact implies that immanent concepts are of no empirical use in this case. Exceptionally, the researcher could prefer functional concepts. According to Constantinesco, Zweigert and K?tz's functional concepts are too broad and ill-defined. Contrary to these concepts, immanent concepts are useful in fine-tuning the perspective of investigation. It is even possible to form immanent concepts for shared differences between legal systems. I will show this advantage of immanent concepts in view of two different methods for protecting needy family members against disinheritance: the first method is to secure a sum of money; the second method is to limit the testamentary power by provisions which guarantee a certain share in the estate. The second method is that of the 'legal portion' of the Civil law. The comparatist can limit his subject matter to the 'Pflichtteilsberechtigter' in German law and the 'Noterbe' in Austrian law. 'Pflichtteil' in German law only creates an obligation to pay a substitute in money for the value of the share which an heir has in the heritage. The same is true for the 'Noterbe' in Austria. The comparatist can also limit his subject matter to the 'Pflichtteilsberechtigter' in Swiss law and the 'réservataire' in French law. The same German word 'Pflichtteil' means something else in Swiss law: in Swiss law the 'Pflichtteil' is part of the heritage itself; it is not the value of a share in the heritage. In Switzerland the 'Pflichtteil' is the guaranteed part of the heritage that is not at the disposal of the deceased. Furthermore, the Swiss 'Pflichtteil' is equivalent to the French 'réserve', i.e. that part of the wealth of the deceased that is reserved for certain heirs.(14) This example confirms two important statements: (1) terminological resemblance does not guarantee any conceptual correspondence fixing the comparability of the rules of different legal systems, a statement which has been elaborated in subsection 3.1 above; (2) immanent concepts make it possible to look at similar specifications that legal systems give to their national concepts. The second statement implies that Constantinesco is right in his assertion that Zweigert and K?tz's functional concepts are too broad and ill-defined. The formation of functional concepts pays only general attention to the intention of legal rules, e.g. the intention of a part of a heritage to provide for the needs of certain heirs. 4. Comparative concepts on the Internet 4.1 The Index to Foreign Legal Periodicals The Index to Foreign Legal Periodicals is a bibliography which is available on the Internet.(15) The Index gives access to the contents of selected legal periodicals, excluding all types of source publications. The Index covers several countries, excluding the United States, the British Isles, the British Commonwealth, whose jurisdictions have a Common law basis. Nevertheless, the Index covers a large range, about 30 per cent, of Common law articles. The Index uses English keywords since the majority, about 70 per cent, of its subscribers are in Common law jurisdictions.(16) The editors of the Index to Foreign Legal Periodicals pretend to provide the researcher with an internationally acceptable legal terminology in English. However, the keywords of the Index to Foreign Legal Periodicals have been criticized. The English keywords of the Index evoke associations with Common law terminology since they follow, as far as possible, the keywords of the Index to Legal Periodicals covering Anglo-American periodicals only. As a consequence, the presentation of continental European law is more difficult than with, for example, French keywords. René David,(17) the famous scholar of comparative law, was convinced that a formulation of the keywords in French instead of in English would have done much to increase the popularity and diffusion of the Index to Foreign Legal Periodicals in continental law countries. According to David, French keywords would have been understood immediately. The editors of the Index to Foreign Legal Periodicals prefer uniform keywords expressing non-specialized functional concepts. However, these keywords are too broad being based on Zweigert and K?tz's functional concepts. Functional concepts go without the precision of legal concepts. For example, with the keyword 'judicial review of administrative acts', there is no distinction whether the legal protection is guaranteed by administrative courts or ordinary courts.(18) Besides, functional concepts have to be stated in sentences belonging to everyday language like the 'judicial review of administrative acts' mentioned above. The keywords of the Index are merely a modest step towards a comparative thesaurus which could improve the retrieval of relevant documents on the Internet. 4.2 Comparative thesauruses? Information concerning different legal systems is available on the Internet. The use of the Internet could facilitate comparative research by a wide audience. However, the large range of search engines on the Internet does not contain satisfactory indexing. The lack of precision of the search engines stresses the importance of any effort at the creation of a real comparative thesaurus since the Index to Foreign Legal Periodicals has the drawbacks mentioned above. A really comparative thesaurus may reduce the amount of irrelevant information. Specifically, a comparative thesaurus enabling standardized indexing for the Internet could be an area of practical application of immanent concepts. Comparative thesauruses consist of normalized relations between the terms selected. These characteristics of comparative thesauruses deserve some explanation. With the aid of comparative thesauruses, documents relating to foreign legal concepts, for instance 'full adoption', may be retrieved by starting from the concept of 'limited adoption' if the broader term 'adoption' connects the specific thesaurus terms. The first term refers to Dutch and French documents, the last one to Austrian and French documents. The two narrower terms and the broader term owe their generality to the immanent concepts mentioned in subsection 3.3. Similarly, immanent concepts could be usefully employed in comparative thesauruses on the Internet. Specific concepts like 'full adoption' or 'limited adoption' may enhance the relevance of documents found by comparatists who want to limit their subject matter. However, it is difficult to find general terms which overcome the terminological differences in the formulation of particular concepts, depending on the legal system concerned. The Anglo-American bias of the Index to Foreign Legal Periodicals mentioned in subsection 4.1 is an important aspect of the terminological problems which must be solved to express comparative concepts in thesauruses. It should not be allowed that thesaurus terms coincide with legal terms which have a national meaning within their particular legal system. To minimize ambiguity, different things should have different names; e.g. 'family provision' as the English concept of providing for the maintenance of a dependant is misleading if used for indexing continental documents concerning succession. There is a risk of confusing the uniform keyword 'family provision' with the English legal concept in the same words: in England the freedom to make a will is not restricted by something like the 'Pflichtteil' as in Swiss law or a mitigated form of that like in Germany or in Austria. Family provision in England implies an indirect limitation of the freedom to make wills. It is like alimony which a judge orders on the basis of a certain amount that is needed.(19) This method for protecting needy family members against disinheritance is not the same as one of the two methods mentioned in subsection 3.2: to secure a sum of money on the one hand, or the 'legal portion' on the other. Agreements based on comparative studies are needed to coin an internationally acceptable legal terminology in English. These agreements could be based on immanent concepts developed for use in private international law, e.g. 'movable' and 'immovable'. These categories are different from the categories of the strictly internal law, i.e. 'personalty' and 'realty'. The use of the distinction of 'movable' and 'immovable' property makes international agreements possible since this distinction is accepted outside the English legal system.(20) International agreements are needed to use up completely the possibilities of communication offered by the Internet. So far, the usefulness of immanent concepts is dependent on the co-operation of scholars of different countries. 5. Conclusions There are three forms of comparative concepts: immanent, extensional and functional. So far, the literature does not answer the question of whether comparative legal studies benefit from the use of either immanent, extensional or functional concepts. The comparability assumption is a device to settle this question because this assumption asks for comparative concepts of empirical use. Comparative studies may use their own concepts of empirical use which use is contingent on the assumption that legal rules from different systems are comparable. The choice of the perspective of concepts cannot be avoided but the comparability assumption containing concepts has to be tested on the legal systems to be compared. Constantinesco's extensional concepts do not determine the intension which provides the comparatist with the key to access to the legal rules to be compared. Terminological resemblance does not guarantee any conceptual correspondence fixing the comparability of the rules of different legal systems. The formation of extensional concepts must be strongly discouraged. By contrast, the formation of functional or immanent concepts may result in comparative concepts which are of empirical use. However, Zweigert and K?tz are wrong in claiming that comparative concepts are completely independent of national concepts. Zweigert and K?tz's functional concepts have their drawbacks since their functional approach rests upon several simplifying assumptions concerning the relationship between law and society. Immanent concepts being partially dependent on national concepts may be of empirical use. In particular, they are useful in fine-tuning the perspective of comparative investigations. Functional concepts do not have this advantage. However, immanent concepts are of no empirical use if the hierarchies of legal systems are too divergent conceptually. Exceptionally, the researcher could prefer functional concepts. This article relates to the direct usefulness of comparative concepts for comparative legal studies on the one hand, and their indirect usefulness in one area of application, on the other. It is concluded that, both for research purposes and in comparative thesauruses on the Internet, immanent concepts are more useful than Zweigert and K?tz's functional concepts. The Internet could offer an incentive to develop a system of immanent concepts to provide for conceptual query tools. Additional agreements are needed to coin internationally acceptable legal terms in English in order to express rather parallel notions. References Bell, A.P. (1989), Modern Law of Personal Property in England and Ireland (London/Edinburgh: Butterworths). Constantinesco, L.-J. (1974), Traité de droit comparé, Tome II: La méthode comparative (Paris: Librairie générale de droit et de jurisprudence). David, R. (1960), 'Review: Index to Foreign Legal Periodicals', Law Library Journal, 53(3), 234-35. David, R. (1980), English Law and French Law (London/Calcutta: Stevens & Sons/Eastern Law House). Drobnig, U. (1969), 'Methodenfragen der Rechtsvergleichung im Lichte der "International Encyclopedia of Comparative Law"', in E. von Caemmerer, S. Mentschikoff und K. 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(1980), General Problems of Private International Law (Alphen aan den Rijn/Rockville: Sijthoff & Noordhoff). Kokkini-Iatridou, D. et al. (1988a), Een inleiding tot het rechtsvergelijkende onderzoek (Deventer: Kluwer). Kokkini-Iatridou, D. (1988b), 'The Tertium Comparationis in the Micro-Comparative Research', in Law in East and West: On the Occasion of the 30th Anniversary of the Institute of Comparative Law, Waseda University (Tokyo: Waseda University), 231-42. Mellema-Kranenburg, T.J. (1988), De legitieme portie (diss.) (Deventer: Kluwer). North, P.M. and J.J. Fawcett (1992), Cheshire and North's Private International Law, 12th edn. (London/Dublin/Edinburgh: Butterworths). Van Laer, C. (1997), Het nut van comparatieve begrippen, Ius Commune Europaeum 20 (diss.) (Antwerpen/Groningen: Intersentia). Zweigert, K. und H. K?tz (1996), Einführung in die Rechtsvergleichung, 3. neubearbeitete Auflage (Tübingen: J.C.B. Mohr). -------------------------------------------------------------------------------- Notes 1. Dr Coen van Laer (1952) studied law and philosophy at the University of Nijmegen. The author is law librarian in Maastricht, the Netherlands, and chief editor of the Dutch journal De Juridische Bibliothecaris. He publishes regularly in the fields of comparative law, jurisprudence and librarianship. Correspondence address: Maastricht University, University Library, P.O. Box 616, 6200 MD Maastricht, the Netherlands. E-mail: c.vanlaer@ub.unimaas.nl 2. Mrs Marieke Oderkerk (comparatist, Utrecht) kindly read earlier drafts. I have gratefully made use of her comments. 3. Netherlands Civil Code, book 5, section 106, subsection 3: 'Onder appartementsrecht wordt verstaan een aandeel in de goederen die in de splitsing zijn betrokken, dat de bevoegdheid omvat tot het uitsluitend gebruik van bepaalde gedeelten van het gebouw die blijkens hun inrichting bestemd zijn of worden om als afzonderlijk geheel te worden gebruikt.' (translated by P.P.C. Haanappel and E. Mackaay) 4. 'Wohnungseigentum ist das Sondereigentum an einer Wohnung in Verbindung mit dem Miteigentumsanteil an dem gemeinschaftlichen Eigentum, zu dem es geh?rt.' (Par. 1 Gesetz über das Wohnungseigentum und das Dauerwohnrecht; see http://sunsite.informatik.rwth-aachen.de/germlaws/weg/p1.html) 5. 'Wer eine fremde bewegliche Sache einem anderen in der Absicht wegnimmt, dieselbe sich rechtswidrig zuzueignen, wird ... bestraft.' (Par. 242 Strafgezetzbuch; see http://sunsite.informatik.rwth-aachen.de/germlaws/stgb/p242.html; translated by J.J. Darby) 6. Constantinesco (1974, 23-24, 36-37, 67 footnote 38, 78-79, 88, 123, 318). 7. Kokkini-Iatridou et al. (1988a, 131-132); Kokkini-Iatridou (1988b, 235-236). 8. Zweigert and K?tz (1996, 11, 33, 43). 9. Constantinesco (1974, 86 footnote 121, 314); cf. Constantinesco (1974, 38, 323), where he implicitly rejects the functional approach. 10. Drobnig (1969, 225, 228-230; 1972, 124-126; 1977, 28-30). 11. Eltzbacher (1900, 47, 51). 12. Article 356: 'L'adoption confère à l'enfant une filiation qui se substitue à sa filiation d'origine; l'adopté cesse d'appartenir à sa famille par le sang, ...' Article 364: 'L'adopté reste dans sa famille d'origine et y conserve tous ses droits, ...' These articles are available via http://www.legifrance.gouv.fr (translated by J.H. Crabb). 13. Bell (1989, 19); David (1980, 35). 14. Ferid and Firsching (1982-1990, Grundzüge F); Mellema-Kranenburg (1988, 142-143). 15. See http://www.law.berkeley.edu/iflp/ for general information. 16. According to an electronic message (5 February 1998) from T.H. Reynolds, general editor, to the author of this article. 17. David (1960, 235). 18. G?dan (1992, 150). 19. Herbots (1993, 318); Mellema-Kranenburg (1988, 143). 20. Kahn-Freund (1980, 229); North and Fawcett (1992, 46, 779).