What is Friendship is a book of dialogues on the subject of friendship. Noted Irish Wauthor and philosopher Stephen J. Costello interrogates the great philosophers from Plato and Aristotle through St. Augustine and Montaigne and on to C. S. Lewis, Sartre and Derrida in an effort to understand the nature and function of friendship. Dr Costello lets each philosopher speak in his own words. Here are some of the questions he asks them: ‘What do we love when we love our friends?’ ‘Is like drawn to like?’ ‘What is the relationship between friendship and happiness?’ ‘Is a friend another self?’ ‘Is it possible to love a friend too much?’ ‘What happens when a friend dies?’ ‘Is all friendship self-serving?’ ‘Would you lie for a friend?’ ‘Die for a friend?’ After the fourteen dialogical explorations on the philosophy of friendship that comprise this book, Stephen Costello offers his own philosophico-Christian vision of friendship in the conclusion. This is an inspiring book, one that is full of fascinating insights on an intriguing subject that is surely of relevance to everyone whose lives are made full by their loving-friendships, with their perils and pains as well as their joys and jubilations. For life without friendship is void of meaning.