It is very difficult to speak of enlightenment with detail or precision. Buddhists, Christians, Hindus, Taoists, Sufis, and Jewish mystics all describe enlightenment experiences. Are all such experiences the same? So long as you practice sincerely regardless of the path, any experience which gives you a more profound view of life, and which has a powerfully positive effect on your character can be called enlightenment.
But these experiences differ in their depth, and in this sense, they cannot be said to be exactly the same. Even the same person will experience different levels of enlightenment at different times.
In Buddhism there are nine levels of samadhi. The first level is not true samadhi but rather a pre-samadhi stage. At this level you are clearly aware of the environment, yet you are not aware of your own existence. There is simply no separation between yourself and the world. There is no sense of big or small, external or internal, good or evil. Your mind is completely relaxed and in a state of delight. You feel no suffering, no tension, no vexation. Although this is only the pre-samadhi states, it is a very good experience. Some people already call this stage enlightenment and there is nothing wrong with this.
One level higher than pre-samadhi is initial samadhi. This is the first stage that is considered genuine samadhi. In this state there is a very cool expansive feeling accompanied by radiant light and beautiful sounds. You feel that time and space do not exist. People who reach this level are attached to meditation because they desire this "joy of samadhi." It would be very difficult for them to obey a command not to meditate.
Many people would also be tempted to call this initial samadhi stage enlightenment. However, from the Buddhist point of view this is not genuine enlightenment, at least, not deep enlightenment. But if people want to call it enlightenment, there is nothing seriously wrong with it.
I have just described the first of eight levels of genuine samadhi, which is called "the stage when samadhi arises and you feel happiness and contentment." I will not go into the other seven levels now. But it is important to know that there are many levels of samadhi. In fact, even the experience of pre-samadhi would be of great help to us in life.
So it is quite all right for people who have been dramatically changed by these experiences to call it enlightenment. I do not want to negate their significance. I just want to emphasize to the serious practitioner that this is just the beginning.
Is it possible to say what genuine enlightenment is? Indeed, if Shakyamuni Buddha described himself as enlightened then he would not really be a Buddha because a Buddha would not have such a thought. Actually, Shakyamuni only claimed to have found a way for sentient beings to liberate themselves from suffering. Besides, any description of enlightenment would be inadequate since it would use language, and enlightenment transcends language.
Finally, it can even be said that there is really no such thing as genuine enlightenment, only various kind of experiences that seem to correspond more or less to an ideal. Nevertheless, we refer to it because in teaching the Dharma, it seems to be necessary. We have to point to a goal even if we can't describe it.
How do you establish a real foundation that can lead to enlightenment? Very simply, you must start from the beginning and go through a process of training and practice. After a long while this may culminate in what can be called "gradual enlightenment." When you reach that point, however, that single dramatic event can be considered "sudden enlightenment." It's like going on a trip; you have to take the first step before you can reach your goal. But after many steps, suddenly you are there.
There's no reaching a distant goal without taking many steps. In this sense there is no such thing as sudden enlightenment if by that is meant leaping right into it with no work or preparation. Nevertheless, there have been many who had no prior practice, yet got enlightened very quickly. Others practice for a whole lifetime without results. Why is this?
When enlightenment comes very quickly, we call it "sudden enlightenment;" when it takes a long time we call it "gradual enlightenment." We say that people who get enlightened quickly have sharp karmic roots, and people who do not, have dull karmic roots. Where do these distinctions between sudden and gradual, sharp and dull come from?
In Buddhism we believe that the time span of a life includes one's past as well as future lives. When we meet someone with sharp karmic roots, we believe that they must have practiced diligently in past lives to have such good karma. Such people have a good chance of becoming enlightened in this life, or some life in the near future.
Conversely, we believe that people of dull karmic roots did not practice too well in prior lives, but may sharpen their karmic roots by being diligent now. Taking into account that a person's history spans over many lives, we can see there is really no diffference between sudden and gradual enlightenment or sharp and dull karmic roots. It is a very gradual process that sometimes ripens very quickly, in a flash of joyous awakening. So, as Buddhists, we believe that the fruition of practice depends on how diligently one has practiced in both the past and the present.
The important thing is whether people believe in rebirth. This belief is often difficult to accept in its entirety even among practicing Buddhists. But those who do not believe in rebirth have no way of explaining the differences in people's achievements in the practice. They can merely imagine that some are more fortunate than others. From the standpoint of a single life, yes, there is good and bad fortune. But from the standpoint of many lives over eons of time, the force of karma applies equally to all. This is the law of karma, of cause and effect.
I would like to illustrate at least two stages of enlightenment by relating two stories. The first appears in the Platform Sutra of the Sixth Patriarch. It goes like this: At one time the Sixth Patriarch Huineng was staying at a certain temple. Two young monks were observing a flag on a pole. One monk said, "See how the flag moves in the wind!" The other responded, "No, the flag can't move, it is the wind that is moving." The Sixth Patriarch, overhearing this debate said, "Neither flag nor wind moves. Mind is moving." Upon hearing this, the two monks realized his meaning. What level of enlightenment does this remark indicate?
The first monk's remark that the flag was moving is a simplistic observation. The second monk, who said that the wind was moving, at least had some scientific knowledge. But the sixth Patriarch tried to help them reach a higher stage with his remark. I just now talked about the pre-samadhi stage, when the mind was already stationary. The world still exists then, but you sense no distinction between yourself and the world.
So it is at this stage that your mind and everything else is unmoving. The Sixth Patriarch was in effect telling the monks they should practice harder, since their perceptions were off the mark. After experiencing the pre-samadhi state, one will realize that it is the mind that moves, not external objects.
In the pre-samadhi state the mind is not moving. However, it still exists. This means that the practitioner has not yet reached a genuinely enlightened state. A genuine enlightenment corresponds to the state of no-mind, and that is the same thing as no self. The mind moving corresponds to a very narrow sense of self, or small self. The mind not moving corresponds to a very expanded sense of self, or large self. From the point of view of Chan, only the state of no-mind is the beginning of genuine enlightenment.
How is this no-mind different from the states of samadhi? There's a great difference because throughout the nine states sensation still exists; even in the highest stage there is a sensation of nothingness—no time, no space, no thoughts. People who reach this stage may very well feel that they have attained ultimate liberation, but this very feeling knows that their mind still exists. A person who practices well but without any good guidance may reach the ninth level of samadhi and mistake this for final liberation. In the state of true enlightenment, however, there is no feeling of being liberated, nor is there a feeling of not being liberated.