From now on, every time you note, the object noted and the mind that notes it appear two separate things. You come to know that the material form like the rising and falling is one thing and the mental state that notes it is another. Ordinarily, the material form and the mind that cognizes it do not seem separate. They seem one and the same thing. Your book knowledge tells you they are separate but your personal feeling has them as one. Shake your index finger. Do you see the mind that intends to shake? Can you distinguish between that mind and the shaking? If you are sincere, the answer will be No. But to the meditator whose mindfulness and concentration are well developed the object of attention and the awareness of it are as separate as the wall and the stone that is thrown to it.
The Buddha used the simile of the gem and the thread (D i 72). Just as when you look at a string of lapis lazuli you know: the gem is threaded on a string; this is the gem, this is the string the gem is threaded on, so does the meditator know: this is the material form, this is the consciousness that is aware of it, which depends on it, and is related to it. The Commentary says that the consciousness here is the insight consciousness, insight knowledge, that observes the material form. The lapis lazuli is the material form and the string is the consciousness that observes. The thread is in the gem as the insight awareness penetrates the material form.
When you note rising, the rising is one thing, the awareness is one thing - only these two exist. When you note falling, the falling is one, the awareness is one - only these two. The knowledge comes clear to you of its own accord. When you lift one foot in walking, one is the lifting, the other is the awareness - only these two exist. When you push it forward, the pushing and the awareness. When you put it down, the putting down and the awareness. Matter and awareness. These two only. Nothing else.
As your concentration improves further, you understand how the material and mental things you have been noting keep passing away each in its own time. When you note rising, the form rising comes up gradually and passes away. When you note falling, the form falling comes up gradually and then passes away. You also find that the rising as well as the awareness passes away, the falling as well as the awareness passes away. With every noting you find only arising and passing away. When noting bending, one bending and the next do not get mixed up. Bends, passes away, bends, passes away - and thus, the intention to bend, the form bending, and the awareness, come and go each in its time and place. And when you note the tiredness, hotness, and pain, these pass away as you are noting them. It becomes clear to you: they appear and then disappear, so they are impermanent.
The meditator understands for himself what the commentaries say: "They are impermanent in the sense of being nothing after becoming." This knowledge comes to him not from books nor from teachers. He understands by himself. This is real knowledge. To believe what other people say is faith. To remember out of faith is learning. It is not knowledge. You must know from your own experience. This is the important thing. Insight meditation is contemplation in order to know for yourself. You meditate, see for yourself, and know - this alone is insight.
Regarding contemplation on impermanence the commentary says:
" ... the impermanent should be understood."
" ... impermanence should be understood."
" ... the discernment of the impermanent should be understood."
Visuddhi Magga, i. 281
This brief statement is followed by the explanation: "Here, impermanent are the five Aggregates." You must know that the five aggregates are impermanent. Although you may not understand it by your own knowledge, you should know this much. Not only that. You should know that they are all suffering, all without a self. If you know this much, you can take up insight meditation. This understanding made by learning is given in Culatanhasankhay Sutta:
"If, O lord of devas, a monk has heard, All states are not fit for adherence, he understands all the truth."
To "understand" means to meditate on the mind and matter and be aware of it. It is the basic insight knowledge of Analytical Knowledge of Mind and Matter and the knowledge by Discerning Conditionality. So, if you have learnt that mind and matter are all impermanent, suffering and not self, you can begin meditating from the analysis of mind and matter. Then you can go on to higher knowledges like the investigating knowledge.
"Understanding all the states, he comprehends all of them."
So, the least qualification required of a beginner in insight meditation is that he must have heard or learnt of the impermanent, suffering, and not self nature of mind and matter. To Buddhists in Burma this is something they have had since childhood.
We say mind and matter are impermanent because they come to be and then pass away. If a thing never comes to be, we cannot say it is impermanent. What is that thing which never comes to be? It is a concept.
Concepts never come to be, never really exist. Take a personal name. It comes into use from the day a child is named. It appears as though it has come to be. But actually people just say it in calling him. It has never come to be, it never really exists. If you think it exists, find it.
When a child is born, the parents give it a name. Suppose a boy has been named "Master Red." Before the naming ceremony the name Master Red is unknown at all. But from the day the boy is named people begin calling him, Master Red. But we cant say the name has come into being since then. The name Master Red just does not exist. Lets find it out.
Is the name Master Red in his body? On his head? On his side? On his face? No, it is not anywhere. The people have agreed to call him Master Red and that is all. If he dies, the name die with him too? No. As long as the people do not forget it, the name will live on. So it is said, "a name or surname never gets destroyed." Only when the people forget it will the name Master Red disappear. But it is not destroyed. Should someone restore it, it will come up again.
Think of the Bodhisattas names in the Jatakas: Vessantara, Mahosadha, Mahajanaka, Vidhura, Temiya, Nemi ... these names were known in the times of the stories but were lost for millions of years until the Buddha restored them. Four asankheyvas and a hundred thousand kalpas ago the name Dipankara the Buddha and the name Sumedha the recluse were well known. They were lost to posterity afterwards. But our Buddha restored them and the names are known to us again. They will be known as long as the Buddhas teaching lasts. Once Buddhism is gone from earth these names will be forgotten too. But if a future Buddha were to speak about them again, they would become known again. So, concepts, names are just conventions. They never exist. They have never been and they will never be. They never arise, so we cant say they "pass away." Nor can we say they are impermanent. Every concept is like that - no existence, no becoming, no passing away, so no impermanence.
Nibbana, although it is a reality, cannot be said to be impermanent because it never comes to be or passes away. It is to be regarded as permanent because it stands as peace for ever.