Abstract：A unique feature of continental civil law is its basic division of real rights and creditor’s rights. The cause of this division，however，seems to have escaped the attention of legal scholars for generations，even centuries. This study provides a plausible explanation for this fundamental feature of continental civil law. Specifically，in continental law countries the basic structure of transactions and contracts is a division into two distinct rights: real rights and creditor’s rights. Real rights are defined by physical units，whereas creditor’s rights are defined with respect to interpersonal relations or personal behavior. For instance，in the simple transaction of buying a newspaper，the buyer assumes real rights over the newspaper and the seller obtains creditor’s rights over the payment. Creditor’s rights are defined with respect to the creditor，but the same legal relationship can also be defined with respect to the debtor，in which case it is called the debtor’s obligations. In the example above，the buyer of the newspaper bears the debtor’s obligations over the payment. It is evident that creditor’s rights and debtor’s obligations are two sides of the same coin. In the following analysis，the term creditor’s rights are used in most of the discussion，but debtor’s obligations are used where warranted． This inquiry is meaningful for several reasons. First，it hopes to provide an intuitive，straightforward，sound，and convincing answer to the question of why continental civil law developed this structure. The reasoning is based on the idea of letting ″the evidence speak for itself.″ Second，we use relevant materials from other social sciences to help illustrate the division，as insights from non-legal sources can shed light on legal issues. The major thrust of the analysis can be summarized as follows. The fundamental reason for continental civil law’s twin-right structure is that transactions are often associated with a time lag. If no time lag is involved，there are no enforcement problems and consequently there is no need to separate real rights and creditor’s rights （to deal with any enforcement problem）. When information is complete，a transaction is completed in a split second，as no searching or bargaining is needed; furthermore，there will be no enforcement problems. In other words，when transaction costs are zero，transactions are completed instantaneously and no enforcement problems will ensue，as the idea of ex post has been ruled out by definition. As there are no enforcement problems，no concepts are needed to deal with any possible transaction imperfections. This simply means that in a world of zero transaction costs，the ideas of real rights and creditor’s rights would never have been developed. The very reason why the twin concepts are needed is because we live in a world of positive transaction costs，where transactions are normally not completed in a split second and a certain portion of transactions inevitably result in enforcement problems. To deal with enforcement problems，the concepts of real rights and creditor’s rights have been developed in the continental law tradition． In other words，if，and that is indeed a big if，transactions are all conducted in kind and a double coincidence occurs at each and every trade，then no money is needed. Similarly，if transactions are all completed instantaneously （i.e.，there are no enforcement problems） then there is no need to develop the concepts of real rights and creditor’s rights. Conversely，the mere existence of real rights and creditor’s rights suggests that certain interests in transactions have not been properly dealt with，and this in turn implies that a time lag exists between the point that such rights become relevant and the time that the （interests of） rights are properly realized or at least dealt with.
