All boundaries simultaneously include and exclude, and in so doing they simultaneously confer and deny. Citizenship, with its many elements, imposes an array of boundaries upon groups of all sorts, from populations to demoi. Upon inspection, citizenship and its attendant semi-citizenships appear to behave like a piece of mercury that divides and rejoins itself under varied political circumstances. The disaggregation of nationality scatters people all over the spectrum of fundamental rights. Other forms of semi-citizenship clump larger bundles of rights together in one quadrant. Each instance of semi-citizenship presented in this book describes a group of persons living within the boundaries of a liberal democracy who have some, but not all, of the rights and status associated with full citizenship in that state. Each can be traced back through the history of the nation-state. None are recent aberrations that reflect anomalies of contemporary politics. Most examples also appear to carry a similar form throughout many, if not all, liberal democratic states. Some of the statuses in question confer nationality, some have temporary residence, and some only the most shadowy identity within the nation-state system. Many, but by no means all, offer opportunities and freedoms not associated with full membership alongside the disadvantages of partial inclusion. None are recognized with a formal legal status that connotes the existence of permanent categories of partial membership.