"The world is so full of a number of things,
I'm sure we should all be as happy as kings."
This couplet from Robert Louis Stevenson is a miracle of succinct and teasing whimsy. On the face of it, it seems like a joyous celebration of the earth's plenitude, a delight in the endless possibility of life. Yet the word should is a shadow on all this exuberant wonder. In spite of the multitude of things, how many of us are happy? Including, of course, the kings themselves. Perhaps the point is the ironic self-defeat of materialism, the inevitability of what the economists call scarcity: the number of things that exist is always lower than the number required to satisfy human desire. If I was going to scrawl anything across the nursery wall in large curly letters it would be this, but perhaps I would thus condemn my children to a slow and numbing realisation of the real scarcity of happiness.