What is a Citizen?

What does it mean to be a citizen? The claim of liberal political thought represented most directly by John Locke, is that the state is an association of individuals with natural rights who contract with one another to protect those rights to life, liberty, and property in a peaceful society. For Rousseau, the citizen in the ancient sense is no longer possible, and instead, we must look for standards in nature to form citizens of the world. But for Aristotle, and for many of us today, citizenship is membership in a political community that entails duties and responsibilities and requires dedication to a common good that benefits the individual and the community as a whole.