Re: kiai in aikido?
What if while you are practicing Kiai, you are actually learning Aiki? Take the cup analogy. Fill the cup with water, and it is full. In order to put more water in, you have to take some out. Now say there are rules, one of being, the cup must always be full. Since the cup has a finite volume, any water you project out must replaced. The more forcefully you project water out, the more water you must replace it with. So where you see the act of yelling to project Ki or practice Kiai, what you don't see, is the flow of KI throughout.
To just yell loud, is not necessarily Kiai. for a proper Kiai yell, you must muster power, or be internalizing at hara, as you are projecting in your technique and your yell. The more powerfully you project, the more you must also internalize. So as where I see Kiai and Aiki as kind of opposites, they are used simultaneously to compliment each other. They phase and fade like the speakers in THX system to achieve the desired effect. In Aikido, we seek to harmonize Aiki and Kiai to achieve a desired effect. Because you are using one, doesn't mean the other isn't there. They are concepts that play off each other and aid each other so that the end result is a flowing technique.
So to Practice Kiai, is to practice Aiki; and to do so in such a manner to harmonize the flow of Aiki and Kiai, is Aikido.