From Cervantes to Samuel Beckett, the novelist picks out the writers who portray true friendship as an antagonistic businessLars Iyer is a lecturer in philosophy at the University of Newcastle upon Tyne. He is the author of two books on Blanchot (Blanchot's Communism and Blanchot's Vigilance: Phenomenology, Literature, Ethics) and his blog Spurious. He has also written two novels, Spurious and, published by Melville House, Dogma.Buy Dogma at the Guardian bookshop"'In your friend you should possess your best enemy', Nietzsche writes. What a remarkable thing to say! This is a concept of friendship radically different from the smugly narcissistic friendship collectives of Facebook. Nietzsche's true friend is someone who challenges you deeply, who badgers, bothers, enrages, and insults you – ...