This paper defends the functional theory of citizenship on the grounds of the conceptual map of contemporary models of citizenship that I have developed elsewhere. I address three different types of criticisms. First, the focus is on the arguments of those who believe the legal model of citizenship needs to be abandoned or rejected all together. Several reasons against this suggestion are highlighted. Second, a short discussion follows of some points made by those contributors to this volume who instead think that the legal model should be not be rejected, but that it still needs to be amended or requires development to fit contemporary migration patterns. Finally, I address the criticisms of those who believe the whole enterprise of developing a general theory of citizenship is flawed since there would be no concept of citizenship independently of political contingencies.