1. The reality of the body may be imagined by contemplation, but to experience it directly, one must work with vedana (bodily sensations) arising within it.
2. Similarly, the actual experience of the mind is attained by working with the contents of the mind. Therefore, as body and sensations cannot be experienced separately, the mind cannot be observed apart from the contents of the mind.
3. Mind and matter are so closely interrelated that the contents of the mind always manifest themselves as sensations in the body. For this reason the Buddha said-
Vedanasamosarana sabbe dhamma.vedanasamosarana sabbe dhamma3
Whatever arises in the mind is accompanied by sensations.
Therefore, observation of sensation offers a means-indeed the only means-to examine the totality of our being, physical as well as mental.
There are four dimensions to our naturefour dimensions to our nature-the body and its sensations and the mind and its contents. These provide four avenues for the establishing of awareness in satipatthana. In order for the observation to be complete, every facet must be experienced, as it can by means of vedana. This truth-exploration will remove the delusions we have about ourselves. Likewise, to come out of the delusions about the world outside, the truth about the contact of the outside world with our own mind-and-matter phenomenon must be explored. The outside world comes in contact with the individual only at the six sense doorssix sense doors-the eye, ear, nose, tongue, body and mind. As all of these sense doors are contained in the body, every contact of the outside world is at the body level. According to the law of naturelaw of nature, with every contactcontact there is bound to be sensation. Every time there is a contact with any of the six sense objects, a sensation will arise on the body. Therefore, just as the understanding of vedana is absolutely essential to understand the interaction between mind and matter within oneself, the same understanding of vedana is essential to understand the interaction of the outside world with the individual.
If this exploration of truth were to be attempted by contemplation or intellectualisation, we could have easily ignored the importance of vedana. However, the crux of Buddha's teaching is the necessity of understanding the truth not merely at the intellectual level, but by direct experience. For this reason, vedana is defined as follows-
Ya vedayati ti vedana, sa vedayita lakkhana, anubhavanarasa...4
That which feels the object is vedana; its characteristic is
to experience, its function is to realize the object....
However, merely feeling the sensations within is not enough to remove our delusions. Instead, it is essential to understand ti-lakkhanati-lakkhana (the three characteristics) of all phenomena. We must directly experience aniccaanicca (impermanence), dukkhadukkha (suffering), and anattaanatta (substancelessness) within ourselves. Of these three, the Buddha always gave importance to anicca because the realisation of the other two will easily follow when we have experienced deeply the characteristic of impermanence. In the Meghiya Suttameghiya sutta of the Udana, he said-
Aniccasannino hi, Meghiya, anattasanna santhati, anattasanni asmimanasamugghatam papunati dittheva dhamme nibbanam5
In him, Meghiya, who is conscious of impermanence the consciousness of what is substanceless is established. He who is conscious of what is substanceless wins the uprooting of the pride of egotism in this very life, that is, he realizes nibbana.
Therefore, in the practice of satipatthana, the experience of anicca, arising and passing away, plays a crucial role.
The Mahasatipatthana Sutta begins with the observation of the body. Here several different starting points are explained-observing respiration, giving attention to bodily movements, etc. It is from these points that one can progressively develop vedananupassana, cittanupassana and dhammanupassana. However, no matter where the journey starts, everyone must pass through certain stations on the way to the final goal. These are described in important sentences repeated not only at the end of each section of kayanupassana but also at the end of vedananupassana, cittanupassana and each section of dhammanupassana. They are-
1. Samudaya-dhammanupassi va viharati.
2. Vaya-dhammanupassi va viharati.
3. Samudaya-vaya- dhammanupassi va viharati.6
1. One dwells observing the phenomenon of arising.
2. One dwells observing the phenomenon of passing away.
3. One dwells observing the phenomenon of arising and passing away.
These sentences reveal the essence of the practice of satipatthana. Until and unless these three levels of anicca are practised, one will not develop wisdom. Therefore, in order to practise any of the fourfold satipatthana, one has to develop the constant thorough understanding of impermanence, known as sampajanna in Pali. In other words, one must meditate on the arising and passing away of phenomena (anicca-bodha), objectively observing mind and matter without reaction. The practice of samudaya-vaya-dhamma (impermanence), should not be merely a contemplation or process of thinking or imagination or even believing; it should be performed with paccanubhotipaccanubhoti, (direct experience). Here the observation of vedana plays its vital role, because with vedana a meditator very clearly and tangibly realizes samudaya-vaya (arising and passing away).7 Sampajanna in fact is knowing the arising and passing away of vedana and thereby all four facets of our being.
It is for this reason that in each of the four satipatthanas, sampajano, as well as atapiatapi (ardent) and satimasatima (aware) are essential qualities and the three are invariably repeated for each of the satipatthanas. And as the Buddha explained, sampajanna is observing the arising and passing away of vedana.8 Hence the part played by vedana in the practice of satipatthana should not be ignored; or this practice of satipatthana will not be complete.
In the words of the Buddha-
Tisso ima, bhikkhave, vedana. Katama tisso? Sukha vedana, dukkha
vedana, adukkhamasukha vedana. Ima kho, bhikkhave, tisso vedana.
Imasam kho, bhikkhave, tissannam vedananam, parinnaya cattaro
satipatthana bhavetabba.9
Meditators, there are three types of bodily sensations. What are the three? Pleasant sensations, unpleasant sensations and neutral sensations. Having completely understood these three sensations, meditators, the four-fold satipatthana should be practised.
The practice of satipatthana is complete only when one directly experiences impermanence. Body sensations provide the nexus where the entire mind and body are tangibly revealed as an impermanent phenomenon leading to liberation.

Notes: (All references VRI edition)

1. Digha Nikaya 2.373
2. Loc. cit
3. Anguttara Nikaya 3.8.83
4. Dhammasangami Atthakatha 1, Kamavacacarakusalapadabhagamiyam
5. Udana 31
6. Digha Nikaya 2.374
7. Udana 31
8. Samyutta Nikaya 3.5.399 - 400
9. Ibid. 3.5.415