A man I know was setting up some fairly simple but clever device which he put into a tank of water (the proper place for it to achieve its function), explaining its technical details to his wife. I did a similar thing, explaining it to my wife, only I did it rather differently. I think we were at some kind of hands-on workshop or interactive educational event. Then I was in the next room and was asking for a more specific version of something that somebody had said. I said something like "how wide do you mean by wide?" As I asked, I could see two images of my arm which was bent at the elbow and straightening to a degree, and I had the strong impression that they had the same meaning as my words.
THE FOLLOWING IS FOR DREAM NERDS ONLY:
My speculation is that the dream was expressing, in symbolic language, the ideas that human culture may have advanced in some ways over the millennia but that it still hasn't fully evolved past hierarchy (e.g. sexism), and that the ancients weren't so different from modern people as I thought they were. I haven't quite fathomed the part of the dream that took place in the second room, except that my request for a more specific version of what I'd just heard may have reflected a difference between my modern way of thinking and the more poetical, imprecise style of the ancients. The image of straightening arms also bears resemblance to the words of my question "how wide?" Somewhere about halfway between arms open wide and arms folded.
I have no empirical evidence that my interpretation is correct. It just seems to ring true. I suspect that the function of dreams is memory consolidation. I'd been finding answers to an uncommonly large number of questions I've been curious about yesterday (many of which were about the things in my above dream interpretation). Most dreams aren't expressed in a style that's immediately recognisable to my awake mind as stuff I'd be likely to consolidate in memory, which has made me skeptical as to how memory consolidation could possibly be the function of dreams, but I'm beginning to see how it could be so if it were being done in symbols. I suspect that the symbols of dreams are the "machine code language" of an older, more primitive part of the brain which is being used for the process.
It's probably very human to dislike unsolved mysteries and to be much more content with the first plausible theory that comes to mind as the correct one. So I may have fallen into a trap like Freud did, though I didn't bring sex into it, which proves it's a different trap, if it's a trap at all.