Koan practice is taken up by Roshis Kapleau and Eido in the next two chapters, so the treatment here will be brief. A koan is an account of an incident between a master and one or more disciples which involves an understanding or experience of enlightened mind. A koan usually, but not always, involves dialogue. When the original incident is remembered and recorded, it becomes a "public case," which is the literal meaning of koan. Often what makes the incident worth recording is that the disciple's mind, if only for an instant, transcends attachment and logic, and he catches a glimpse of emptiness or Buddhanature. At that moment there is a "transmission" of Mind between master and disciple. Once, after the Buddha gave a sermon to his senior disciples, he picked up a flower and silently held it up before the assembly. All the monks except one were mystified. Mahakasyapa alone knew the Buddha's meaning, he smiled, saying nothing. Thus the Buddha transmitted to Mahakasyapa the wordless doctrine of Mind. Although this incident preceded the rise of Ch'an by over a thousand years, it exemplifies the spirit of koans.

The earliest koans were spontaneous incidents that arose naturally in the context of practice. During the Sung dynasty (960-l279), Ch'an masters began using these "public cases" as a method of meditation for their disciples. In attempting to plumb the meaning of a koan, one has to abandon knowledge, experience, and reasoning, since the answer is not susceptible to these methods. The student must find the answer by "becoming one" with the koan. Only when there is nothing left in the mind but the koan is awakening possible.

Closely related to the koan is the hua-t'ou (literally "head of a thought"), a question that the meditator inwardly asks himself "What is Mu?" or "Who am I?" are two good examples. As with the koan, the answer is not resolvable through reasoning. The meditator devotes his full attention to asking himself the huat'ou, over and over. His objective is to probe into the source of the question, that is, the state of mind that existed before the question became a thought.