I imagine a child. That child is me. I can reconstruct and vividly remember portions of my own childhood. I can see, taste, smell, feel, and hear them. Then what I do is, not write about that kid or about his world, but start to think of a book that would have pleased him.
What children expect from grownups is not to be 'understood', but only to be loved, even though this love may be expressed clumsily or in sternness. Intimacy does not exist between generations - only trust.
