People use dowsers and dowsing regularly, to ask questions, to find water and food and for other reasons. I have used them myself in my past.
Many within the New Age community would argue that it is the spirit world speaking to them with yes and no answers. A spin to the right for yes and a spin to the left for no, almost like a Ouija board on string.
In science there is another explanation, that being Ideomotor movements. These are muscle movements caused by subconscious mental activity that looks and feels as if the movements are involuntary.
It is subconscious motion outside of the awareness of the subject.
I would add my own theory into this scientific mix.
The subconscious mind (symbolised by the subterranean chambers of the great pyramid of Egypt) is a reservoir of information and it puts together plans and ideas which it runs by the conscious mind!
It deals with automatic movement and subconscious thoughts process faster than conscious thoughts (Thought = Thoth of Egypt).
So could it be, and this is my theory, that when we ask a dowser a question, which science states is our own ideomotor movements, moving the dowser itself, that it is our own reservoir of information,the subconscious mind, that is really answering the question posed by us because it knows the answer to our question?
Our own subconscious mind is causing the dowser to move, by involuntary muscle movements, in the direction that it consciously knows provides the answer for us. Which appears to us to be an outside source but is really an inside source, ourselves!
Could it be that our subconscious mind is connected to the quantum field of quantum data that is forever all around us, the library of universal knowledge, and therefore is an encyclopedia?
I think it could be!