The mirror of mind reflects without interference;
Its vastness and clarity radiate through countless worlds.
Various phenomena all manifest themselves;
To a perfectly illumined one there is neither inside nor outside.
The verses above describe the “no mind” state of Ch’an. If you still feel there is an inside and outside, it is not Ch’an. If you feel everything is within you, that is not Ch’an either. When the mind is not moving, it only appears that there is no mind, but this is not the case. When the mind is not moving, it is still focused on one thought. Therefore, it would be better to call the unmoving mind the “one mind” state. A person who reaches the point where the mind is not moving may feel as if he has no mind, but he is mistaken.
When only one thought remains, the movement of the mind is not noticeable. This is the “one mind” state. In the “no mind” state there is no discrimination ─ no inside or outside, no near or far, no good or bad. A person in the “no mind” state is aware of phenomena, but he is not attached to phenomena. If he were not aware that he was in a “no mind” state, then he would be a fool.
“No mind” is equal to wisdom; “one mind” is not. Similarly, the lower levels of samadhi are not equivalent to wisdom. A person experiencing samadhi may feel he does not discriminate, but in fact he is unaware of a steady stream of subtle discriminations. At the shallowest level of samadhi ─ the first dhyana level ─ one can experience a dozen or so discriminations in one ksana. A ksana is the length of time it takes for one wandering thought to arise, and is equivalent to one sixtieth the time it takes to snap your fingers. In the same span of time, roughly sixty discriminations pass through the ordinary mind.
Only a person in deep samadhi can tell if another person is in samadhi; he can also determine the depth of that person’s samadhi. Samadhi practice is gradual. A practitioner must enter the shallowest level and then slowly deepen his samadhi through practice. As samadhi deepens, the person is able to discern the number and frequency of discriminations that occured at the previous levels. A practitioner in shallow samadhi cannot discern his own state. He may think he has attained “no mind, ” but he is wrong.
— The Sword of Wisdom by Master Sheng Yen (page 141)