Are there any circumstances in which philosophy is not a power game, albeit one that it is conducted according to the most rigid rules, which are intended to direct us toward the truth? Anyone who feels confident enough to answer this question should ponder the words of Xenophanes: 'No one knows, or will ever know, the truth about the gods and everything; for if one chanced to say the whole truth, nevertheless one would never know it.' This accords with much twentieth-century philosophy, as it did with certain elements of Greek philosophy, and has done with skeptical philosophy through the centuries between. Yet if we cannot know the truth, the psychological argument becomes all but irresistible - he who musters the best argument wins. Fortunately we now recognise that philosophy is as much about the rules of this argument as it is about who wins.