Mushin is a Zen term, "Mu" meaning negation or void; "Shin" meaning heart, mind or feeling. Literally "void mind", but a better translation would be "the absence of intellectual/logical mind". The word mushin basically refers to a state of mental clarity and enhanced perception (sensory and intuitive) known as pure mind, produced by an absence of conscious thought, ideas, judgements, emotion (fear and anxiety), pre-conception or self-consciousness. A state of cognitive awareness characterized by the absence of discursive thought. A state of mind in which the mind acts/reacts without hypostatization of concepts. Mushin is often erroneously taken to be a state of mere spontaneity. Although spontaneity is a feature of mushin, it is not straightforwardly identical with it. It might be said that when in a state of mushin, one is free to use concepts and distinctions without being used by them.
Training in any art can only be successful when the person has absorbed the techniques, so that they are so much a part of him or her that using the technique is purely intuitive and unconscious, where no thought processes are required. The person's attitude is one of receptivity, alert, but relaxed and fearless, with no preconceived idea of the outcome. Mushin is said to be the state of mind of the Zen archer just as the arrow flies.
This does not mean to be without thoughts, ideas, feelings, etc., when you face a task. It means letting natural faculties operate in a consciousness free from thoughts and reflections. This state of mind is also known as egolessness. This is often likened to the lunar reflection in water. Neither the moon nor the water has any preconceived idea of producing the incident designated by us as "the moon - in water." The water reflects accurately all images within its range - so a mind as calm as undisturbed water can apprehend all aspects of a project or task and react appropriately.