This essay articulates and defends Aristotle’s argument in Politics 7.4 that there is a rational limit to the size of the political community. Aristotle argues that size can negatively affect the ability of an organized being to attain its proper end. After examining the metaphysical grounds for this principle in both natural beings and artifacts, we defend Aristotle’s extension of the principle to the polis. He argues that the state is in the relevant sense an organism, one whose primary end is to make good reasons available to individuals and promote them as choiceworthy. The size of a polis can affect its ability to perform this function, since growth promotes anonymity among citizens, which in turn frustrates the familiarity between cit...