The meaning and importance of friendship have become questions of increasing interest in recent years, as declining rates of marriage and parenthood have made the family less central and friends more so in the lives of many people, particularly in the western world. Yet the history of friendship, and the ways in which it has changed its form and its meaning over time has only just begun to be discussed. Both historically and in the contemporary world, the language of friendship has not been confined to personal relationships. It is significant also in discussions or descriptions of a range of different ethical systems, social institutions and political alliances. The term 'friend' and others derived from it, such as 'mate' or 'comrade', have played an important role in establishing and characterizing particular religious organization, national cultures and political movements. The concept of friendship has been an important one in western philosophy, too. Indeed, for many philosophers, from Plato and Aristotle to G. E. Moore, friendship, or terms connected to friendship are crucial to the establishment of society and to the meaning of the good life. As Jacques Derrida has argued recently, in relation to his book The Politics of Friendship, while 'friendship ...is marginal in the usual taxonomies of political concepts, as soon as you read the canonical texts in political theory starting with Plato or Aristotle, you discover that friendship plays an organising role in the definition of justice, of democracy even.' This volume aims to combine an analysis of the major classical philosophical texts of friendship and their continuing importance over many centuries with a broader discussion of the changing ways in which friendship was understood and experienced in Europe from the Hellenic period to the present. It is the result of a collaborative research project that has involved philosophers and historians with special research interests in Classical Greek philosophy and in the history of medieval and renaissance, 18th century 19th and 20th century Europe.