Ki and Chi
Okay, first things first: Ki and Chi are one and the same. Japanese and Chinese (respectively) pronunciation of the same character.
Amazing, how much confusion that little things caused.
What is it ya ask?
Ki is the life force of all Existence… yours, mine, everyone’s. Your aura is the manifestation of your personal Ki, your own life force. You could think of it as a single instrument in an infinite orchestra playing an infinite melody… not that I actually think of it in those terms, I just thought it might be a good metaphor. Magick, psi, whatever you want to call it, is in essence, a manipulation of that force. Ki is just a convenient name that is used by martial artists. Magi/occultists (or at least the ones I know) call it "energy".
It is sometimes Polarized Yin or Yang, or Elementally based (Spirit, Earth, Air, Fire, Water… anyone even DREAM of thinking about Captain Planet, and I’ll hunt you down and kill you. That show SUCKED! [sorry ‘bout that]).
But it’s just like EVERYTHING else: different frequencies and wavelengths of that universal whatever… just like light, radio waves, sound and even matter.
The martial artists in Ranma can manipulate their Chi (see I use them interchangeably… not even a conscious choice!) to perform amazing attacks, like the Shishi Hokudan or the (I can’t remember the Japanese) Roaring Tiger Domineering. The former channels depression, the latter channels pride (to my understanding… either way though). It’s just polarized Ki/Chi.
Magick is the exact same… focused Ki/Chi… we who practice (first difference. Occultists "practice", martial artists "use"… both "perform", though) the magickal arts just think of it differently.
Focus, energy, will, and release. In essence, the same.