Ius Filiationis: A defence of Citizenship by Descent 89 some democratic procedure in which they decide whom to admit or reject, nor the mere fact of subjection to the laws due to temporary presence in the territory. All of these rules lead to too much contingency and discontinuity with regard to the composition of the citizenry. Promoting civic attitudes and skills among those who are citizens is important, but it cannot resolve the puzzle who has a claim to be a citizen in the first place. Automatic acquisition of membership at birth and for life sets this question aside. It makes citizenship a part of citizens’ personal identities that they are likely to accept. And it allows democracies to tap into resources of solidarity and to promote a sense of responsibility towards the common good and future generations. In a nutshell, these are my two arguments why a modified version of ius sanguinis should be accepted as necessary for democratic states: In a world of territorial states that control immigration, ius sanguinis (or ius filiationis) is as indispensible as ius soli for protecting the children of migrants. It provides them with the right to stay and to be admitted in their country of birth as well as their parents’ country of origin. No other legal status can secure these rights as well as a birthright to dual nationality. Deriving citizenship from unchosen and permanent features of personal identity – where and to whom one is born – sets aside the politically divisive membership question for the vast majority of citizens, creates a quasi-­natural equality of status among them and signals that membership is linked to responsibilities for the common good and for future generations. No citizenship education programme can fully substitute for these signalling effects of birthright citizenship. Open Access This chapter is licensed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license and indicate if changes were made. The images or other third party material in this chapter are included in the chapter’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the chapter’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.