Mushin is a state of mental clarity, awareness and enhanced perception (both sensory and intuitive). This is known as pure mind, produced by the absence of conscious thought, ideas, judgments, emotion. Free of fear and anxiety and of self-consciousness.
It is a mind that is totally calm — a mind not influenced or caught up in events or others emotion, thus a mind more able to freely perceive and respond.
This mind state is achieved through the process of meditative training. The goal is to enhance awareness and sensitivity, while reducing thought and emotion to allow intuitive and spontaneous action – to let the body, not the thinking or emotional mind, to take charge.
For the Japanese classical warrior (Samurai or Bushi), or the 20th century soldier equivalent, as well as modern martial artists, mushin or clear mind is equally important. On the battlefield it could mean the difference between life and death. The Samurai recognized that the state of mind was an equal partner to technical weapons training. When potential death faces you from multiple directions, awareness had to be encompassing. Recognition of danger and response needed to be instantaneous, the body and weapon fully committed in powerful action without concern for the self or hesitation of thought.
This required the non-conscious mind and the instinctive trained body to be free. No longer inhibited, slowed, distracted, or clogged, the mind was free to fully perceive, respond and commit to action. The mind is not fixed on anything and is open to everything; a mind expanded through the whole body with total awareness of and focus on everything.
Mushin trainning is not considered as a religion but as a meditivate practice and philosphy of simplicity that stresses reduction of ego, where hard, dedicated practice conditions the mind and body (the path) towards self-development. Mediation within these groups is used to condition the mind toward the state of mushin (having nothing to do with religious beliefs or doctrine).
The origin of mushin is related to the Zen practice of zazen, which is performed in a seated, motionless position. Like mushin, it involves a stilling of thought while remaining totally receptive. Zazen is not considered a mental exercise or a form of meditation. It is described as “thought without thought,” a dimension of thought lacking conscious activity. A perfect state of zazen is said to yield satori, or “pure freedom of thought.” This has proven to be a highly effective state of consciousness for fighting, and through it the warriors of ancient Japan perfected the practice of all their martial arts. Consequently, zazen has sometimes been called “the religion of the samurai,” though it is not actually a religion but rather (in martial arts applications at least) a purely practical technique.
Interestingly enough, a well-trained fighter with good mushin and zanshin can usually tell if his opponent is maintaining a similar state of awareness. A momentary break in concentration by one party creates an opening called a suki, during which he cannot respond fast enough to counter a move by an opponent still in a state of mushin.