Who wants to be illegal? Who wants that by moving on this Earth, at a certain point, to be punished for his movement? ‘As human beings, we all inhabit the planet Earth as a shared space’ and we all should have equal entitlements with everyone else, everywhere in the world. This idea is simple and immediately appealing to everyone, everywhere, yet the very fact of saying it invites scorn and ridicule, and those who affirm it are declared naive. A person may indulge for some moments in a vision of a world without borders, of himself being a citizen of the world, yet, in the next moment, to shake his head to ‘remove’ the idea, laughing that it is naive. Or a person may start thinking how it would be like to be a citizen of the world, but he may realise that he alone cannot rethink the current world order and, without laughing, he clings to the existing ways of living, in a world with nation-states with their exclusionary and discriminatory borders, which do not exist for those from the ‘first world’ countries and for those with high purchasing power, no matter from which country. The person has a glimpse that ‘things’ in this world could have been different, but how exactly? He does not know. If this person will turn to political philosophers – those who according to the current division of labour must think and imagine the world in a just way – he will discover that political philosophers laugh themselves at the idea of a citizen of the world. They scorn the idea and refuse to think about it, affirming that it is utopic, or that it will lead to a ‘global despotism’. Political philosophers want to be ‘realistic’ and they build theories without examining the ‘given’ building blocks: nation-states and their borders. In doing so, political philosophy legitimises the nation-state and its exclusionary borders, and thus it ends up making people illegal. The building blocks of political philosophy are the first trap for thinking a just world, and this book starts by examining a fall into this trap.