Each of us gives off a certain "presence." We say that some people have a big presence, whereas others do not. . . . This big presence that is projected is sometimes described in Japan as ki, "life energy" or "spiritual force." A dynamic, positive mental state gives rise to a powerful outward expression of ki — a big presence. Conversely, a negative, withdrawn state of mind creates a concurrent withdrawal of ki. Thus, from moment to moment, situation to situation, the radiation of ki modulates.
— H. E. Davey, Living the Japanese Arts & Ways