If you fail to meditate on the rising phenomena and so do not know their real nature of impermanence, suffering and not-self, you may relive them and thus let defilements be. This is a case of latent defilements. Because they arise from objects, we call them "object latent." What do people cling to and why do they cling to? They cling to things or persons they have seen because they have seen. If you fail to meditate on them as they arise, somehow or other graspings arise. Defilements are latent in whatever we see, hear, taste, etc.
If you meditate, you find that what you see passes away, what you hear passes away. They pass away in no time at all. Once you see them as they really are, there is nothing to love, nothing to hate, nothing to cling to. If there is nothing to cling to, there can be no clinging or grasping.
And you meditate right now. The moment you see, you meditate. You can't put it off. You may buy things on credit, but you cannot meditate on credit. Meditate right now. Only then will the clinging not come up. Scriptural speaking, you meditate as soon as the eye door process ends and before the subsequent mind-door process begins. When you see a visible object, the process takes place like this: First, you see the object that comes up. This is the seeing process. Then you review the object seen. This is the reviewing process. Then you put the forms seen together and see the shape or material. This is the form process. Last of all, you know the concept of name. This is the name process. With objects you have never seen before, and so you do not know the names of, this naming process will not occur. Of the four, when the first or seeing process takes place, you see the present form, the reality, as it rises. When the second or reviewing process takes place, you review the past form, the form seen - reality again. Both attend on reality - the object seen. No concept yet. The difference is between the present reality and the past reality. With the third process you come to the concept of shape. With the fourth you come to the concept of names. The processes that follow are all various concepts. All these are common to people not practised in insight meditation.
There ate 14 thought moments in the process of seeing. If neither seeing, hearing, nor thinking consciousness arises, life continuum goes on. It is identical with rebirth consciousness. It is the consciousness that goes on when you are sleeping fast. When a visible object or any such appears, life continuum is arrested, and seeing consciousness, etc., arises. As soon as life continuum ceases, a thought-moment arises adverting the consciousness to the object that comes into the avenue of the eye. When this ceases, seeing consciousness arises. When this again ceases, the receiving consciousness arises. Then comes the investigating consciousness. Then, the consciousness that determines whether the object seen is good or not. Then, in accordance with the determination reached, moral or immoral apperceptions arise violently for seven thought moments. When these cease, two retentive resultants arise. When these cease, there comes subsidence into life continuum like falling asleep. From the adverting to retention there are thought-moments. All these manifest as one seeing consciousness. This is how the seeing process takes place. When one is well practised in insight meditation, after the arising of life continuum following the seeing process, insight consciousness that reviews "seeing" takes place. You must try to be able to thus meditate immediately. If you are able to do so, it appears in your intellect as though you were meditating on things as they are seen, as they just arise. This kind of meditation is termed in the Suttas as "meditation on the present."
"He discerns things present as they arise here and now." M. iii.227
"Understanding in reviewing the perversion of present states is knowledge in arising and passing away" Patisambhidāmagga
These extracts from the Suttas clearly show that we must meditate on present states. If you fail to meditate on the present, apprehending arises from life continuum. This consciousness arises to review what has just been seen. The thought moments included are: apprehending consciousness 1, apperceptions 7, and registering consciousness 2 - a total of 10 thought moments. Every time you think or ponder, these three types of consciousness and ten thought moments take place. But to the meditator they will appear as one thought moment only. This is in conformity with the explanations in connection with the knowledge of dissolution in Patisambhidāmagga and Visuddhi Magga. If you can meditate beyond the apprehending, you may not get to concepts and may stay with the reality - the object seen. But this is not very easy for the beginner.
If you fail to meditate even at the apprehending, you get to form process and name process. Then graspings come in. If you meditate after the emergence of graspings, they will not, disappear. That is why we instruct you to meditate immediately, before the concepts arise.
The processes for hearing, smelling, tasting, touching, are to be understood along similar lines.
With thinking at the mind door, if you fail to meditate immediately, subsequent processes come up after the thought. So you meditate immediately so that they may not arise. Sometimes, as you are noting rising, falling, sitting, touching, a thought or idea may come up in between. You note it the moment it arises. You note it and it ends right there. Sometimes a wandering of the mind is about to arise. You note it and it quiets down. In the words of some meditators, "it is like a naughty child who behaves himself when shouted at: "Quiet!'"
So, if you note the moment you see, hear, touch, or perceive, no subsequent consciousness will arise to bring about graspings.
"... you will simply have the sight of the thing seen, the sound of the thing heard, the sense of the things sensed, and the idea of the thing cognized."
As this extract from Mālunkya Sutta shows, the mere sight, the mere sound, the mere sense, the mere idea is there. Recall them and only the rea1 nature you have understood will appear. No graspings. The meditator who meditates on whatever arises as it arises sees how everything arises and passes away, and it becomes clear to him how everything is impermanent, suffering, not self. He knows this for himself - not because a teacher has explained it to him. This only is the real knowledge.