The only moving parts are attention and thought. You can cast about in thought, in a sort of file of possible ideas and a few of their interconnections, and come up with something to put attention onto, in the hope of taking attention by surprise so that it opens itself wide. To attend to the thought is to become the thought, to enact it. So a thought is not an image or a gesture but something active, a shaped enactment in meaning. Attention goes through the thought - the thought can only last a certain time, the duration of its movement, and so to sustain the thought you have to repeat it. And if the first few repetitions aren't quite right, they get better until they suddenly go stale and attention which had already darted far ahead withdraws. It's a little game played in the mind, this duet, which isn't a pure duet, it turns out, because it's been on stage the whole time in front of a silent audience who have already anticipated every move. And it seems as if the audience is always there and always off stage, but this can't be true because if it is there it is attention and if its attention its in the play.