There are four main necessities in the Vipassana task-
1. atapi-having arduous endeavour
2. sampajano-realising with right view
3. satima-having mindfulness
4. samadhi-having one-pointed concentration.
The task of Vipassana, of real meditation, is based on these four main necessities. Here samadhi is not directly stated in the Mahasatipatthana Sutta, but according to the commentaries and sub-commentaries, samadhi is included in the term satima.
The Meaning of Sampajanna
The word sampajannasampajanna that we are now going to discuss is also used in terms of pajanatipajanati and sampajano. First of all, we have to know the true meaning of sampajanna. The word sampajanna is derived from the combination of three syllables- sam + pa + janna
sam (rightfully, completely, by oneself)
pa (in different ways and means, specifically)
janna (knowing, realising).
From the viewpoint of terminology, the word sampajanna is defined by commentators and sub-commentators in the above manner.1
Again, from the standpoint of ideological issues, this term is defined in order to have a precise meaning in the following manner-
1. Asammohalakkhanam sampajannam

Unwavering knowledge is the characteristic of sampajanna. It is just like the knowledge of a person who loses his way in a deep forest and finds the right way again.
2. Tiranarasam sampajannamtiranarasam sampajannam
This is the function to implement what one has firmly decided to perform.
3. Pavicayapaccupatthanampavicayapaccupatthanam
The nature of scrutinization appears in the realm of the meditator's mind.2
Different kinds of sampajanna
There are four different kinds of sampajanna-
1. satthaka sampajannasatthaka sampajanna-knowing what is beneficial and what is not.
2. sappaya sampajanna-knowing the appropriate time and situation when it may be beneficial.
3. gocara sampajannagocara sampajanna-always contemplating on the usual meditation objects, whatever posture is assumed or whatever is being done.
4. asammoha sampajannaasammoha sampajanna-having clear, unwavering knowledge of material and mental phenomena in the body and a clear outlook on life and the world.
The first of these four is beneficial in both mundane and supramundane affairs. It is not samatha nor Vipassana, yet an aid to the meditation task. However, in the Visuddhimagga, the first two kinds of sampajanna are called pariharika panna (the wisdom that should always be borne in mind).
The most important one for meditators is the third one, gocara sampajanna. It denotes that, apart from the time when one is asleep, the meditation objects should constantly be contemplated. If one makes the effort to have gocara sampajanna arise ceaselessly, there is no need to make asammoha sampajanna arise; it will appear automatically.
The Arising of Asammohasampajanna
Relating to the term sampajanna, only the state of going backward and forward etc. can be called sampajannapabba. Nevertheless, sampajanna should arise in every situation and at every moment. Concerning the arising of asammoha sampajanna, detailed descriptions are given in the commentaries. The notable facts are as follows-
The body is similar to a cart; the cart itself cannot go alone, it must be drawn by oxen; but the cart and oxen themselves cannot move. Only when the oxen are harnessed to the cart and driven by a cart-driver, can the cart move.
The most important one here is the cart-driver. He is compared with the mind; the oxen are compared with the element of motion (vayo dhatu). The other three elements (tayo mahabhutas) are caused by the mind.
Of these four elements, when walking, the element of kinetic energy (tejo), and the element of motion (vayo) are the leading factors and the element of solidity (pathavi) and the element of fluidity (apo) are just followers. When lying or sitting or standing, pathavi and vayo are leading factors and the remaining two are just followers.
All these explanatory notes are mentioned in the Mahasatipatthana Sutta, Visuddhimagga and Vibhanga commentaries. To evaluate one's situation in meditation, it is necessary to know about them.
When meditating incessantly, by means of gocara sampajanna, the natural happenings of phenomena can automatically be realized more and more deeply, by means of asammoha sampajanna. It may be said that asammoha sampajanna is fulfilled if the following questions can be answered;
1. ko gacchati (Who is going? Who is the one that is going? Is there any creator?)
2. kassa gamanam (Whose action [of going] is it? Is there any creator that creates going?)
3. kim karana gacchati (Why does one go? Why does the action [of going] arise? What is the root cause of [the action of] going?)
These sample questions are just for the case of 'going'. For every case, the questions may arise in the same manner, and the answers should be understood accordingly. From the literary viewpoint, these questions and answers are very long, but in the practical field of work they can be realized in one week, as they are fundamental practices. It is very enjoyable to learn about them.
From the literary point of view again, they are namarupapariccheda-nana and paccayapariggaha-nana, also called nataparinna, and sammasana nana and udayabbaya nana, also called tiranaparinna.3
In the view of the meditator, they are, indeed, very clear.
The Buddha's teaching about the full realisation of the difference between mentality and materiality at the first stage is very clear. It is just like knowing a string of transparent amber beads, differentiating what is string and what are amber beads. The knowledge of a meditator is very clear in view of cause and effect. For example, it is obvious that wanting to go (cause) creates the action of going (effect), paccayapariggaha.4
In order to possess right view, gocara sampajanna should always be established and developed. So as to make sampajanna arise in a quick manner, a system of principles for meditators is prescribed. It is called 'gatapaccagatavatta-constant practice in going and coming'. The principle of this constant practice had been prevailing for 1000 years, from the lifetime of the Buddha up to the Sri Lankan Age. 'The routine duties of a meditator or the principle of constant practice' were performed and practically followed by bhikkhus through the ages, and they were successful in the task of their practice. Detailed accounts of such incidents are mentioned in the commentaries.5
Let me give a small example. When bhikkhus went for their alms-round to the villages and came back to their residence, they had to practise meditation constantly with mindfulness at every step on the way. If they were careless or heedless at ten footsteps, they stepped backwards about ten steps and started meditating from there again. Those who practised regularly in this way could reach the apex of the ariyan stages even in their youth.
Though this is instructed only on the way of alms-round, it should be practised at every moment, even at the time of eating, doing something, going to the lavatory, etc. Therefore, it is said that in Sri Lanka there was no resthouse in which arahantship had not been attained. It is necessary to perform meditation while eating, sleeping, taking a bath, etc.6
In fact, the task of anapana satipatthana is the old common road trodden by every previous Buddha. Only the great noble ones are worthy of this noble task. Na ceva ittaram-it cannot be practised just for a short moment; naca ittarajanasevitam-it is not worthy for the inferior ones; garukam garukabhavanam-it should receive more effort than other subjects of meditation; it is necessary to perform it with deep respect.7 Then the benefit arising out of it can become greater.
In this task of anapana, sati and sampajanna are needed more than in other meditation methods. Therefore the Buddha expounded-
Naham, bhikkhave, mutthassatissa asampajanassa anapanassatim vadami.
I do not give the method of anapana to those who are heedless and careless, devoid of sampajanna.8
May you all develop sampajanna and succeed in your meditation task easily and swiftly!

Notes: [References from VRI edition in brackets]

1. Dhamasangani Atthakatha 175, 192 [VRI 163]; Patisambhidamagga Atthakatha, 1.343 [VRI 1.1.108-109]; Samyutta Nikaya Atthakatha 1.74 [VRI 1.1.38]; Samyutta Nikaya Atthakatha 2.118 [VRI 1.2.73]; Vibhanga-Mulatika 2.180 [VRI 523]; Visuddhimagga-Tika 1.187 [VRI 1.85], Myanmar edition
2. Dhammasangani Atthakatha 1.219 [VRI 163]; Visuddhimagga 1.157 [VRI 1.85]; Mahaniddesa Atthakatha 121, Myanmar edition [VRI 10]
3. Samyutta Nikaya Atthakatha 2.103, Myanmar edition [VRI 1.2.63]
4. Samannaphala Sutta Vipassana Nanakatha, Digha Nikaya Atthakatha 1.197-8, Myanmar edition [VRI 1.234 Adayo]
5. Majjhima Nikaya Atthakatha 1.262-3 [VRI 1. 465]; Digha Nikaya Atthakatha 1. 165-182 [VRI 1. 214]; Samyutta Nikaya Atthakatha 3.220-3 [VRI 3.5.368]; Vibhanga Atthakatha 2.332-348 [VRI 523], Myanmar edition
6. Samyutta Nikaya Atthakatha 3.221 [VRI 3.5.368]; Vibhanga-Atthaktha 2.335 [VRI 523], Myanmar edition
7. Visuddhimagga 1.276 [VRI 1.230], Myanmar edition
8. Majjhima Nikaya 3.127 [VRI 3.149], Anapanassati Sutta; Majjhima Nikaya-Atthakatha 4. 100 [VRI 3. 149], Myanmar edition