Re: Aikido: The learning of natural movement
I partly agree with your thoughts Eric, and also David's, although my following analogy only touches the outskirts of what constitutes "ki" phenomena in a physical sense. Imagine one's body constantly buffetted by randomly-varying forces from each and every direction on each and every portion of our surface (let's leave out the soft parts like eyes, ear channels, nose, groin and so on for a start). In such an environment, it is entirely possible that many people will quickly pick up at a young age the "natural" way to let the body absorb such a force spectrum in the best possible way (i.e., to minimize injury and stress on individual parts), and also will build up requisite sinews, muscle and bone, and develop breathing and behaviour to enable existence in such a hostile environment. Learning how to move where one wishes to (to the best of one's ability), directly if one can, indirectly if not feasible with given conditions, is perhaps analogous to the idea of moving from center, with ki, etc. Negating another person's power has no analogue here, since the external forces have sources far beyond our power to negate. However, if the sources are close-by and human, they will be affected by our action/reaction, and can be negated (or turned against the them) because the human is also only using another source (ground and/or gravity) to create a force on us.
In the absence of such an environment, clearly most people never learn such a mode of movement, nor develop their bodies for it. Exercises for this development exist, as Mike Sigman, Robert John, Dan Harding and others have in several cases explicity described, and their practice is gruelling, exactly because the hostile environment I described above (or a vastly more complex superset thereof) is being mentally duplicated and simulated.