Enlightenment is discussed in books, but it does seem to be unclear exactly what constitutes enlightenment, and how difficult it is to achieve it. Some books or people make it seem like it is a simple thing to accomplish. Whether enlightenment is easy or difficult to achieve depends on the practitioner.

One discourse in the Buddhist texts describes sixteen different types of enlightenment. There are experiences where one has not actually seen the true nature. There are experiences where one does see the true nature, but the experience recedes. And then there is great enlightenment, which is complete and permanent.

Many of these so-called enlightenment experiences are physiological and psychological responses which rise in the body and mind as a result of practice. Some people feel a sense of joy, or feel that the body and mind have been liberated. Are these true enlightenment experiences? No, not according to Ch'an.

They are just feelings, emotional states. However, they are valuable experiences. It's permissible to call these enlightenment experiences, because during such times the person's mind is different than it usually is. The mind is brighter, and for a while the person may have no vexation. But after a few days, hours, or even minutes, the person will encounter something that gives rise to greed or aversion, and again vexations will appear.