1 Adoption, between the best interest of the child and the wishes of the adopters Carlos Martínez de Aguirre Professor of Civil Law University of Saragossa (Spain). 1. Adoption is a legal figure that basically consists of the establishment of a legal relationship between two persons, similar to the one existing between biological parents and their children. The scope of adoption has varied throughout history, and has moved closer to (or further away from) biological filiation according to time and place, and to the purposes assigned to adoption by legal or political institutions as well. Adoption can be (and historically has been) used for multiple purposes: individual, social, political, familial, hereditary and religious. Any of these purposes may have an institutional meaning, i.e., may be endorsed by the law. These purposes need to be consistent to each other, however, they also mainly need to be consistent with the institutional purpose of adoption: so, the law may identify a basic purpose for adoption (e.g., that of protecting abandoned children as in current Spanish law), and the adopters can have a different, subjective, purpose (e.g., having a child), that has to be consistent with the institutional one. Nowadays, the establishment between two persons of a legal relationship that is totally or only partially similar to that existing between parents and their biological children, remains as the most central and characteristic feature of adoption. On the other hand, biological filiation has always been the template for adoptive filiation, and so remains today. Hence it has been usual, since Roman Law, to refer to adoption as an imitation of nature (“adoptio enim naturam imitatur”), or as a purely legal image of the legal and natural filiation relationship. Thus, it is important to underline that adoption creates a relationship that can be identified as "filiation" owing to its resemblance to the biological relationship of parent and child, while at the same time it serves the purposes assigned to it by law. These basic ideas are useful not only to identify the scope of adoption, but also, to a certain extent, to identify its limits: what might be called the "tolerance limits" of adoption (i.e., the limits whose overflowing causes the disfigurement of the legal institution itself). Law may not create biological links, but it may create legal links similar to those existing between parents and their biological children. This juridical similitude is almost complete in