“The basic idea is very simple. You make up an imaginary world that you would enjoy being in, and then you imagine yourself walking around in this world. Not much different, in principle, than what people do in any ordinary daydream. But here the idea is to work for consistency, so that it appears the same every time you enter it, and to continually add details to it. With practice and familiarity, this imaginary world will begin to take on a sense of being a ‘real’ place; not real in the same way as the physical world, but having a permanence about it nonetheless.”