A tremendous burden is being placed on friends. Individuals want friends more than family. Couples want to marry a friend - a very novel idea. And at the social level, politicians, sociologists, even bishops realise that in the anonymity of the networked age, friendship is increasingly important to care, commitment and belonging.

Friendship, we believe or hope, is elastic enough to connect us across the web of complex lives, and strong enough not to snap. But is it? For whilst many are turning to friendship, few are asking what they are turning to.

In this new, accessible philosophy of friendship, Mark Vernon examines the love called friendship upon which so much happiness depends. He links the resources of the philosophical tradition with numerous illustrations from modern culture to ask about friendship and sex, work, politics and spirituality. Unusually, he argues that Plato and Nietzsche, as much as Aristotle and Aelred, should be put centre stage. Their penetrating and occasionally tough insights are invaluable if friendship is to be a full, not merely sentimental, way of life for today.

In this new version of his book previously published as The Philosophy of Friendship, Mark Vernon also tackles friendship and the internet exploring the rise of social networking sites and asking how notions of friendship may or may not be changing, for good or ill, because of the internet. He also adds a chapter on the psychology of friendship, looking at notions of friendship that arise from evolutionary psychology.