Where do we get our sense of justice and fairness from? Is it hardwired in us? Are we nakedly self-interested creatures, or are we, at least partially, altruistic? These are questions philosophers - from Plato to Hobbes, from Rousseau to David Hume - have pondered for hundreds of years. And a famous game invented by economists- called The Ultimatum Game - may help provide some of the answers. All this is up for discussion and debate this week in The Philosopher's Arms. Welcome to the Philosopher's Arms - a place where philosophical ideas, logical dilemmas and the real world meet for a chat and a drink. Each week Matthew Sweet takes a thought experiment with philosophical pedigree and asks why it matters in the everyday world. En route we'll learn about the thinking of such luminaries as Aristotle, Hume, Kant and John Stuart Mill. And all recorded in a pub in front of a live audience, ready to tap their glasses and demand clarity. Questions we might confront along the way include: should the government put Prozac in the water supply? How should I treat my daughter if it turns out she's a robot? And is there anything morally wrong with having sex with a supermarket chicken? These will lead us into discussions about the treatment of mental illness, the structure of financial markets, and subjects as varied as happiness, infidelity and homosexuality. Our assumptions and intuitions will be challenged and, perhaps, undermined. Producer: David Edmonds.