One of the most misunderstand subjects concerning an understanding of Aikido is the meaning of “aiki.”
“Ai,” as the verb “au,” means “to agree with, to match, to fit.” As a contraction of the verb “awasu,” “ai” means to join, to unite, to combine.
“Ki,” means “mind, will, turn of mind, spirit.”
Accordingly, if one had no more information than this, one could think that “aiki” meant “to unite the minds or spirits.” In fact, the “aiki” of “Aikido,” is often translated as “harmonizing spirits,” even though the more proper word for harmony is “hei,” as in the word “hei-wa,” “peace.” Unfortunately, this is incorrect, because it ignores the unique meaning that old jujutsu texts gave to “aiki,” and which must have influenced Ueshiba’s selection of this term.
These texts treat “aiki” and “kiai” as two sides of the same mental state, a condition in which two minds are united as one, in such a manner that the stronger mind controls the weaker mind. “Kiai” implies the active state of one’s mind, whereas “aiki,” the passive state. “Kiai” is a condition of one’s mind in which one’s “ki” or mental energy is actively concentrated upon an object. “Aiki” is the state of one’s mind in which this mental force is quiescent. “Kiai” is the motive power which prompts a person to action with the strong resolve to carry it to a successful conclusion.It is the force which furnishes the impulse to take advantage of an opportunity.
The Japanese believed that “kokoro” (mind, heart) commanded the “ki” and this “ki” caused the “chikara” (force, strength) to execute this command. This, of course, is the Japanese understanding of the Chinese theory that the “yi” (mind, intent) dictates to the “chi” (internal energy) which moves the “li” (external strength). I do believe, however, that in his later years, Ueshiba changed the emphasis of his Aikido as well as reinterpreted the term aiki to imply harmony, peace, and divine love. This, however, does not change the accepted meaning of this term in Japanese martial arts.