Hilary Mantel has a really excellent essay in the Guardian Review, "Beyond black: questions of belief". Here's a little bit of it, about her orientation towards the psychics she saw perform:
I was not immune from fellow-feeling. Which other self-employed persons stand up in public to talk about non-existent people? Novelists, of course. We listen to non-existent voices and write down what they say. Then we talk with passion and conviction about people no one can see. Our audiences are complicit, of course, whereas the audiences for professional psychics are ambivalent. They teeter on the edge of delusion and the edge of derision. For the psychic, it's a no-win situation. If she gets it wrong, she's rubbish. If she gets it right, she's a cheat. One of the things I learned while writing the book is that scepticism can be held as firmly, devoutly, illogically as any religious position. Elaborate edifices of fraud are proposed - so elaborate, so unlikely, that it's easier to believe that, after all, the dead are speaking.