Uh, OK. So what is the metaphor of the sphere and what does it mean in relation to the body? I have never heard of this metaphor and have no idea what it refers to, and I'm probably not the only one. I have no way of knowing that there is a metaphor relating the body to a sphere unless someone says so...
My point in responding to the question about the sphere with a comment about different models of the sphere is that -- it depends what you mean by a sphere and it depends what you mean by stability. I.e., more info is needed to answer the question of whether a sphere is stable.
Personally I usually find mechanical models clear and metaphors just confusing unless I already know what the metaphor is talking about. So I often have no clue what people are talking about until they stop using metaphors and tell me directly what they mean. I have met people who were the opposite.
Here is some (possibly) relevant stuff - keep in mind that this is the product of my own personal rantings and ravings, and certainly that I certainly do not
and can not
speak for Dan:
Morihei Ueshiba, Budo and Kamae - Part 3 - More on six directions...