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 Kotz'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 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 Kotz'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 mmanent 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 sharedComparative 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 Kötz'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 Kötz'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