To stimulate his imaginary world he will pick up something that wobbles and run around watching it wobble talking to himself.. you can see him transporting himself into another world. He gets very self conscious if he catches you looking at him and he only does it in front of people he trusts. He told me this.
The other part of his life is spent trying to comprehend the world through what I would call productive inquiry. He asks lots of questions which elicit responses from the people around him.
I was burning some dead wood in the woodland area at the bottom of the garden when he came and we spent a very pleasant couple of hours chatting and feeding the fire with wood, then going off and doing something else and coming back and making the fire grow again from the ashes. We talked about all sorts of things, school, his friends, his forthcoming birthday, other countries, fire, family, the topics are endless and that is one of the nice things about talking to children - their minds are completely fluid.. there doesn't have to be a logic or reason for talking about something.
When I look back on the afternoon I realised that more or less everything we did and said was, from his point of view, learning to comprehend the world a little better.. apart from the time he wobbled of course..