All conditioned realities that arise and fall away can be classified as five khandhas, aggregates. The five khandhas are not different from the three paramattha dhammas which are citta, cetasika and rūpa.
Realities classified by way of five khandhas
The Buddha discovered the truth of all phenomena. He knew the characteristic of each phenomenon by his own experience. Out of compassion he taught other people to see reality in many different ways, so that they would have a deeper understanding of the phenomena in and around themselves. When realities are classified by way of paramattha dhammas (absolute realities), they are classified as: citta, cetasika, rūpa, nibbāna.
Citta, cetasika and rūpa are conditioned realities (sankhāra dhammas). They arise because of conditions and fall away again; they are impermanent. One paramattha dhamma, nibbāna, is an unconditioned reality ((asankhata dhamma); it does not arise and fall away. All four paramattha dhammas are anattā, non-self.
Citta, cetasika and rūpa, the conditioned realities, can be classified by way of the five khandhas. Khandha means 'group' or 'aggregate'. What is classified as khandha arises because of conditions and falls away again. The five khandhas are not different from the three paramattha dhammas which are citta, cetasika and rūpa. Realities can be classified in many different ways and thus different names are given to them.
The five khandhas are:
1. Rūpakkhandha, which are all physical phenomena.
2. Vedanākkhandha, which is feeling (vedanā).
3. Saññākkhandha, which is remembrance or ''perception'' (saññā).
4. Sankhārakkhandha,comprising fifty cetasikas (mental factors arising with the citta).
5. Viññānakkhandha, comprising all cittas (89 or 121).
All cetasikas classified as three khandhas
As regards the fifty-two kinds of cetasika which may arise with citta, they are classified as three khandhas: a cetasika which is feeling (vedanā) is classified as one khandha, the vedanākkhandha; the cetasika which is remembrance or ''perception'' (saññā) is classified as one khandha, the saññākkhandha; as regards the other fifty cetasikas, they are classified altogether as one khandha, the sankhārakkhandha. For example, in sankhārakkhandha are included the following cetasikas: volition or intention (cetanā), attachment (lobha), aversion (dosa), ignorance (moha), loving kindness (mettā), generosity (alobha) and wisdom (paññā). All defilements and all good qualities are included in sankhārakkhandha, they are impermanent not ''self''. Sankhārakkhandha is sometimes translated as ''activities'' or ''mental formations''.
All cittas are one khandha
As regards citta, all cittas are one khandha: viññānakkhandha. The Pāli terms viññāna, mano and citta are three terms for the same reality: that which has the characteristic of knowing or experiencing something. When citta is classified as khandha the word viññāna is used. Thus, the five khandhas are grouped as one rūpakkhandha, and four nāmakkhandha. Three nāmakkhandhas are are cetasika and one nāmakkhandha is citta.
Khandhas are impermanent
Anything which is khandha does not last; as soon as it has arisen it falls away again. Although khandhas arise and fall away, they are real; we can experience them when they present themselves. Nibbāna, the unconditioned dhamma which does not arise and fall away, is not a khandha.
The ‘visuddhimagga' (XX,96) explains about the arising and falling away of nāma and rūpa:
There is no heap or store of unarisen nāma rūpa (existing) prior to its arising. When it arises it does not come from any heap or store; and when it ceases it does not go in any direction. There is nowhere any depositor in the way of a heap or store or hoard of what has ceased. But just as there is no store, prior to its arising, of the sound that arises when a lute is played, nor does it come from any store when it arises, nor does it go in any direction when it ceased, nor does it persist as a store when it has ceased, (''Kindred Sayings'' IV, 197), but on the contrary, not having been, it is brought into being owing to the lute, the lute's neck, and the man's appropriate effort, and having been, it vanishes - - so too all material and immaterial states (rūpa and nāma), not having been, are brought into being, having been, they vanish.
Khandhas can be experienced
The khandhas are realities which can be experienced. We experience rūpakkhandha when, for example, we feel hardness. This phenomenon does not stay; it arises and falls away. Rūpakkhandha is impermanent. Not only rūpas of the body, but the other physical phenomena are included in rūpakkhandha as well. For example, sound is rūpakkhandha; it arises and falls away, it is impermanent.
Vedanākkhandha (feeling) is real; we can experience feelings.
Vedanākkhandha comprises all kinds of feeling. Feeling can be classified in different ways. Sometimes feelings are classified as threefold: pleasant feeling, unpleasant feeling, indifferent feeling.
Sometimes they are classified as fivefold. In addition to pleasant feeling, unpleasant feeling and indifferent feeling there are: pleasant bodily feeling painful bodily feeling Bodily feeling is feeling which has bodysense, the rūpa which has the capacity to receive bodily impressions, as condition; the feeling itself is nāma, but it has rūpa (bodysense) as condition. When an object contacts the bodysense, the feeling is either painful or pleasant; there is no indifferent bodily feeling. When the bodily feeling is painful it is akusala vipāka (the result of an unwholesome deed), and when the bodily feeling is pleasant it is kusala vipāka (the result of a wholesome deed).
Bodily feeling and mental feeling
Since there are many different moments of feeling arising and falling away it is difficult to distinguish them from each other. For instance, we are inclined to confuse bodily pleasant feeling which is vipāka and the pleasant feeling which may arise shortly afterwards together with attachment to that pleasant bodily feeling. Or we may confuse painful bodily feeling and unpleasant feeling which may arise afterwards together with aversion. When there is bodily pain, the painful feeling is vipāka, it accompanies the vipākacitta which experiences the unpleasant object impinging on the bodysense. Unpleasant (mental) feeling may arise afterwards; it is not vipāka, but it accompanies the akusala citta with aversion, and thus it is akusala. The akusala citta with aversion arises because of our accumulated aversion (dosa). Though bodily feeling and mental feeling are both nama, they are entirely different kinds of feelings, arising because of different conditions. When there are no more conditions for dosa there can still be painful bodily feeling, but there is no longer unpleasant (mental) feeling. The arahat, the perfected one who has eradicated all defilements, may still have akusala vipāka so long as his life has not terminated yet, but he has no aversion.
We read in the Kindred Sayings (I, Sagāthā-vagga, the Māra-suttas, chapter II, par. 3, The Splinter):
Thus have I heard: The Exalted One was once staying at Rājagaha, in the Maddakucchi, at the Deer-preserve. Now at that time his foot was injured by a splinter. Sorely indeed did the Exalted One feel it, grievous the pains he suffered in the body, keen and sharp, acute, distressing and unwelcome. He truly bore them, mindful and deliberate, nor was he cast down...
Feeling classified by way of the contacts
Feelings are sixfold when they are classified by way of the contacts occurring through the six doors: there is feeling which arises because of what is experienced through the eyes, the ears, the nose, the tongue, the bodysense and the mind. All these feelings are different; they arise because of different conditions. Feeling arises and falls away together with the citta it accompanies and thus at each moment feeling is different.
We read in the 'Kindred Sayings' (IV, Salāyatana-vagga, Part II, Kindred Sayings about Feeling, par. 8, Sickness II) that the Buddha said to the monks:
…Monks, a monk should meet his end collected and composed. This is our instruction to you.
...Now, monks, as that monk dwells collected, composed, earnest, ardent, strenuous, there arises in him feeling that is pleasant, and he thus understands:
'There is arisen in me this pleasant feeling. Now that is owing to something, not without cause. It is owing to this contact. Now this contact is impermanent, compounded, arisen owing to something. Owing to this impermanent contact which has so arisen, this pleasant feeling has arisen: How can that be permanent?' Thus he dwells contemplating the impermanence in contact and pleasant feeling, contemplating their transience, their waning, their ceasing, the giving of them up. Thus as he dwells contemplating their impermanence... the lurking tendency to lust for contact and pleasant feeling is abandoned in him.
So also as regards contact and painful feeling...contact and neutral feeling... There are still many more ways of classifying feelings. If we know about different ways of classifying feelings it will help us to realize that feeling is only a mental phenomenon which arises because of conditions. We are inclined to cling to the feeling which has fallen away, instead of being aware of the reality of the present moment as it appears through eyes, ears, nose, tongue, bodysense or mind. In the passage of the 'Visuddhimagga' which was quoted above (XX, 96) nāma and rūpa are compared to the sound of a lute which does not come from any 'store' when it arises, nor goes in any direction when it ceases, nor persists as a 'store' when it has ceased. However, we cling so much to feelings that we do not realize that the feeling which has fallen away does not exist any more, that it has ceased completely. Vedanākkhandha (feeling) is impermanent.
Perception is one khandha
Saññākkhandha (perception) is real; it can be experienced whenever we remember something. There is saññā with every moment of citta. Each citta which arises experiences an object and saññā which arises with the citta remembers and 'marks' that object so that it can be recognized. Even when there is a moment that one does not recognize something citta still experiences an object at that moment and saññā which arises with the citta 'marks' that object. Saññā arises and falls away with the citta; saññā is impermanent. So long as we do not see saññā as it really is: only a mental phenomenon which falls away as soon as it has arisen, we will take saññā for self.
The fifty cetasikas
Sankhārakkhandha (the fifty cetasikas which are not vedanā and saññā) is real; it can be experienced. When there are beautiful mental factors (sobhana cetasikas) such as generosity and compassion, or when there are unwholesome mental factors such as anger and stinginess, we can experience sankhārakkhandha. All these phenomena arise and fall away; sankhārakkhandha is impermanent.
Clinging to khandhas I
Viññānakkhandha (citta) is real; we can experience it when there is seeing, hearing, smelling, tasting, experiencing tangible object through the bodysense or thinking. Viiññānakkhandha arises and falls away; it is impermanent. All sankhāra dhammas (conditioned phenomenal), that is, the five khandhas, are impermanent.
Sometimes the khandhas are called the 'groups of grasping' (in Pāli: upādānakkhandha). The upādānakkhandhas are the khandhas which are the objects of clinging. Those who are not arahats still cling to the khandhas. We take the body for self; thus we cling to rūpakkhandha. We take mentality for self; thus we cling to vedanākkhandha, to saññākkhandha, to sankhārakkhandha and to viññānakkhandha. If we cling to the khandhas and do not see them as they are, we will have sorrow. So long as the khandhas are still objects of clinging for us, we are like people afflicted by sickness.
We read in the 'Kindred Sayings' (III, Khandha-vagga, the First Fifty, par. I, Nakulapitar) that the housefather Nakulapitar, who was an old, sick man, came to see the Buddha at Crocodile Haunt in the Deerpark. The Buddha said to him that he should train himself thus: 'Though my body is sick, my mind shall not be sick. 'Later on Sāriputta gave him a further explanation of the Buddha's words:
Herein, housefather, the untaught many-folk... who are unskilled in the worthy doctrine, untrained in the worthy doctrine - - these regard body as the self, they regard the self as having body, body as being in the self, the self as being in the body. 'I am the body', they say, 'body is mine', and are possessed by this idea; and so, possessed by this idea, when body alters and changes, owing to the unstable and changeful nature of the body, then sorrow and grief, woe, lamentation and despair arise in them. They regard feeling (vedanā) as the self… They regard perception (saññā) as the self... They regard the activities (sankhārakkhandha) as the self… They regard consciousness (viññāna) as the self… That, housefather, is how body is sick and mind is sick too.
And how is body sick, but mind not sick? Herein, housefather, the well-taught ariyan disciple... regards not body as the self, regards not the self as having body, nor body as being in the self, nor self as being in the body. He says not "I am body'', he says not "body is mine'', nor is possessed by this idea. As he is not so possessed, when body alters and changes, owing to the unstable and changeful nature of body, then sorrow and grief, woe, lamentation and despair do not arise in him. He regards not feeling (vedanā) as the self... He regards not perception (saññā) as the self... He regards not the activities (sankhārakkhandha) as the self... He regards not consciousness (viññāna) as the self... As he is not so possessed, when consciousness alters and changes, owing to the unstable and changeful nature of consciousness, sorrow and grief, woe, lamentation and despair do not arise in him. Thus, housefather, body is sick, but mind is not sick.
Clingiln to khandhas II
So long as we are still clinging to the khandhas we are like sick people, but we can be cured of our sickness if we see the khandhas as they are. The khandhas are impermanent and thus they are dukkha (unsatisfactory).
We read in the 'Kindred Savings' (III, Khandha-vagga, Last Fifty, par. 104, Suffering) that the Buddha taught to the monks the four noble Truths: the Truth of dukkha, the Truth of the arising of dukkha, the Truth of the ceasing of dukkha, the Truth of the way leading to the ceasing of dukkha.
He said: Monks, I will teach You dukkha, the arising of dukkha, the ceasing of dukkha, the way leading to the ceasing of dukkha. Do you listen to it. And what, monks, is dukkha? It is to be called the five khandhas of grasping. What five? The rūpakkhandha of grasping, the vedanākkhandha of grasping, the saññākkhandha of grasping, the sankhārakkhandha of grasping, the viññanakkhandha of grasping. This, monks, is called dukkha.
And what, monks, is the arising of dukkha? It is that craving... that leads downward to rebirth... the craving for feeling, for rebirth, for no rebirth... This, monks, is called the arising of dukkha.
And what, monks, is the ceasing of dukkha? It is the utter passionless ceasing, the giving up, the abandonment of, the release from, the freedom from attachment to that craving... This, monks, is called the ceasing of dukkha.
And what, monks, is the way going to the ceasing of dukkha? It is this Ariyan Eightfold Path… This, monks, is the way going to the ceasing of dukkha. So long as there is still clinging to the khandhas there will be the arising of the khandhas in rebirth, and this means sorrow.
If we develop the Eightfold Path we will learn to see what the khandhas really are. Then we are on the way leading to the ceasing of dukkha, which means: no more birth, old age, sickness and death. Those who have attained the last stage of enlightenment, the stage of the arahat, will be, after their life-span is over, free from the khandhas.