Dreaming is half a thought.

There was a book called the Dream Frontier that suggested dreams are just thoughts without subjects. That is, if the thought were, "he goes to the store," it would only have, "goes to the store." The person doing the thinking is implied, because you are in the dream world. The way the authors said it was that it's like Jeopardy: Answers without questions. You need to figure out the question.

Thinking can take the same form, with one exception. While there are often interjections and half-sentences in self-dialog, there is still a real physical world around you to ground you in reality. That could be why we don't become totally immersed in our thoughts. There are also half-realities where we start to think in confabulations, as discussed elsewhere (Sorry I lost the source on that one).

The mind can be a lot more creative when it is not fettered by the need to make a complete thought. What's produced may resonate more, while making a bit less sense.