The Buddha spoke about realities as elements in order to remind us that they are impermanent and not self. When we speak about elements we usually think of the elements in chemistry or physics which have each their own characteristics. In chemistry and physics matter is analysed into elements, but it may seem strange to us to regard the eye or seeing as elements. We are not used to consider them as elements because we are inclined to take them for 'self'. 

What we take for self are only nama-elements and rupa-elements which arise because of their appropriate conditions and then fall away again. Eyesense is only an element which has its own characteristic and is devoid of self ; it is rupa which arises because of conditions and then falls away again. Seeing is only an element which has its own characteristic and is devoid of self ; it is nama which arises because of conditions and falls away again. 

ln the Buddha's teachings realities are classified as elements, some of which are rupa and some of which are nama. When they are classified as eighteen elements; they are as follows:

     The five senses:
         1.  eye-element (cakkhu-dhatu)
         2.  ear-element (sota-dhatu)
         3.  nose-element (ghana-dhatu)
         4.  tongue-element (jivha-dhatu)
         5.  body-element (kaya-dhatu) which is the body-sense
 

     The five objects (experienced through the five senses):
         6.  visible object-element (rupa-dhatu)
         7.  sound-element (sadda-dhatu)
         8.  smell-element (gandha-dhatu)
         9.  taste-element (rasa-dhatu)
        10.  element of tangible objects (photthabba-dhatu),
              comprising the following three kinds of rupa:
             earth-element  (solidity), appearing as hardness or softness
             fire-element  (temperature), appearing as heat or cold
             wind-element, appearing as motion or pressure

     The dvi-panca-vinnanas (experiencing the five sense objects):
        11.  seeing-consciousness-element  (cakkhu-vinnana-dhatu) 
        12.  hearing-consciousness-element (sota-vinnan-adhatu) 
        13.  smelling-consciousness-element (ghana-vinnana-dhatu) 
        14.  tasting-consciousness-element (jivha-vinnana-dhatu)
        15.  body-consciousness-element (kaya-vinnana-dhatu)
 
     Three more elements:
        16.  mano-dhatu or mind-element
        17.  dhamma-dhatu
        18.  mano-vinnana-dhatu or mind-consciousness-element 
 
The five elements which are the five sense-doors are rupa and the five elements which are the objects experienced through the sense-doors are rupa as well. The five elements which are the dvi-panca-vinnanas, experiencing these objects, are
nama. There are two cittas which are cakkhu-vinnana-dhatu, since seeing-consciousness can be kusala vipaka or akusala vipaka. It is the same with the other panca-vinnanas. Thus there are 'five pairs' of citta which are panca-vinnana-dhatu.

The element which is mano-dhatu or mind-element is nama. Mano-dhatu comprises the panca-dvaravajjana-citta (five-sense-door-adverting-consciousness) and the two types of sampaticchana-citta (receiving-consciousness) which are kusala vipaka and akusala vipaka. Thus three kinds of citta are mano-dhatu.

Dhamma-dhatu comprises both nama and rupa. Dhamma-dhatu is the cetasikas, the subtle rupas (sukhuma-rupas) and nibbana.

Mano-vinnana-dhatu or mind-consciousness-element is nama. It comprises all cittas which are not the dvi-panca-vinnanas and not mano-dhatu. For example,
santirana-citta (investigating-consciousness), mano-dvaravajjana-citta (mind-door-adverting-consciousness) and the cittas performing the function of javana such as lobha-mula-citta are mano-vinnana-dhatu.

Panca-vinnana-dhatu (seeing-consciousness-element, etc.), the mano-dhatu (mind-element) and the mano-vinnana-dhatu (mind-consciousness-element) are: vinnana-dhatu (consciousness-element).

Dhamma-dhatu is not identical with dhammarammana (mind-objects). Cittas are included in dhammarammana, but not in dhamma-dhatu, since dhamma-dhatu is: cetasikas, subtle rupas and nibbana. When cittas are classified as elements they are the seven classes of vinnana-dhatu, namely:

Panca-vinnana-dhatu (which are five classes), mano-dhatu (mind-element), mano-vinnana-dhatu (mind-consciousness-element).

Concepts and conventional terms (pannatti) which are included in dhammarammana are not dhamma-dhatu, because they are not paramattha dhammas. Only paramattha dhammas are classified as elements.

Sometimes the Buddha spoke about six elements ; or he classified realities as two elements. There are many different ways of classifying realities, but no matter in which way realities are classified, as khandha, by way of arammana (objects), or in any other way, we should remember the purpose of classifying realities : realizing that what we take for self are only nama-elements and rupa-elements.

In the 'Satipatthana-sutta' (Discourse on the Applications of Mindfulness, Middle Length Sayings I, No.10) we read in the section about mindfulness of the body, that the Buddha spoke about the body in terms of elements. The text states:

And again, monks, a monk reflects on this body
according to how it is placed or disposed in respect
of the elements, thinking: 'In this body there is the
element of extension (solidity), the element of cohesion, the
element of heat, the element of motion.' Monks, even
as a skilled cattle-butcher, or his apprentice, having
slaughtered a cow, might sit displaying its carcass at a
cross-roads, even so, monks, does a monk reflect on this
body itself according to how it is placed or disposed in
respect of the elements, thinking: 'In this body there is
the element of extension, the element of cohesion, the 
element of heat, the element of motion'. Thus he
fares along contemplating the body in the body
internally...and he fares along independently of and
not grasping anything in the world. It is thus too, monks,
that a monk fares along contemplating the body in
the body...

The 'Visuddhimagga' (XI, 30) states:

What is meant? Just as a butcher, while feeding the
cow, bringing it to the shambles, keeping it tied up
after bringing it there, slaughtering it, and seeing it
slaughtered and dead, does not lose the perception
'cow' so long as he has not carved it up and divided
it into parts ; but when he has divided it up and is sitting
there, he loses the perception 'cow' and the perception
'meat' occurs ; he does not think 'I am selling cow'
or 'They are carrying cow away', but rather he thinks
'I am selling meat' or 'They are carrying meat away';
so too this bhikkhu, while still a foolish ordinary
person--both formerly as a layman and as one gone
forth into homelessness--, does not lose the perception
'living being' or 'man' or 'person' so long as he does
not, by resolution of the compact into elements, review
this body, however placed, however disposed, as
consisting of elements. But when he does review it
as consisting of elements, he loses the perception 'living
being' and his mind establishes itself upon elements....

It may not be appealing to see the body as elements. We think of people as 'this man' or 'that woman'. We are not used to analysing what we take for a 'person' in the way we analyse matter, as we do, for example in physics. One might find it crude to think of a body carved up as a cow is carved up by a butcher. However, if we consider the body as it is, there are only elements. Isn't it true that there are solidity, cohesion, temperature and motion? Are these realities 'self', or are they elements devoid of 'self'?

Do the four elements of solidity, cohesion, temperature and motion have anything to do with our daily life? These elements arise all the time. Temperature can appear either as heat or cold; do we not feel heat or cold very often? When we are stung by an insect we can experience the characteristic of heat. We can feel impact of hardness or softness on our body when we are lying down, sitting, walking or standing. Is that not daily life? If we are mindful of the characteristics of the elements more often, we will see things as they are.

The Buddha reminded people of the truth in many different ways. Sometimes he spoke about the body as a corpse in different stages of dissolution. Or he spoke about the 'parts of the body' and he explained how the body is full of impurities,
in order to remind people that what we take for our body are only elements which are devoid of beauty, which are dukkha, impermanent and not self.

We read in the 'Satipatthana-sutta', in the section about mindfulness of the body:

Monks, it is like a double-mouthed provision bag
that is full of various kinds of grain such as hill-paddy,
paddy, kidneybeans, peas, sesame, rice; and a
keen-eyed man, pouring them out, were to reflect:
'That's hill-paddy, that's paddy, that's kidneybeans,
that's peas, that's sesame, that's rice.' Even so monks,
does a monk reflect on precisely this body itself, encased
in skin and full of various impurities, from the soles
of the feet up and from the crown of the head down...

In the 'Discourse on the Manyfold Elements' (Middle Length Sayings III, 115) we read that the Buddha, while he was staying in the Jeta Grove, in Anathapindika's monastery, said to the monks that fears, troubles and misfortunes occur to the fool, not to the wise man. He said to the monks:

'...Monks, there is not fear, trouble, misfortune
for the wise man. Wherefore, monks, thinking,
'Investigating, we will become wise', this is how you
must train yourselves, monks.'

When this had been said, the venerable Ananda
spoke thus to the Lord: 'What is the stage at which
it suffices to say, revered sir: 'Investigating, the monk
is wise'?'
'Ananda, as soon as a monk is skilled in the elements
and skilled in the (sense) fields and skilled in
conditioned genesis and skilled in the possible and the
impossible, it is at this stage, Ananda, that it suffices
to say, 'Investigating, the monk is wise.''

'But, revered sir, at what stage does it suffice to
say, 'The monk is skilled in the elements'?'

'There are these eighteen elements, Ananda: the
element of eye, the element of material shape, the
element of visual consciousness; the element of ear,
the element of sound, the element of auditory
consciousness ; the element of nose, the element of
smell, the element of olfactory consciousness ; the
element of tongue, the element of taste, the element
of gustatory consciousness; the element of body, the
element of touch, the element of bodily consciousness;
the element of mind, the element of mind-objects, the
element of mental consciousness. When, Ananda, he
knows and sees these eighteen elements, it is at this
stage that it suffices to say, 'The monk is skilled in
the elements.' '

'Might there be another way also, revered sir,
according to which suffices to say, 'The monk is skilled
in the elements'?'

'There might be, Ananda. There are these six
elements, Ananda: the element of extension, the
element of cohesion, the element of radiation, the
element of mobility, the element of space, the element
of consciousness. When, Ananda, he knows and sees
these six elements, it is at this stage that it suffices
to say, 'The monk is skilled in the elements.''
'Might there be another way also, revered sir,
according to which it suffices to say, 'The monk is
skilled in the elements'?'

'There might be, Ananda. There are these six
elements, Ananda: the element of happiness, the
element of anguish, the element of gladness, the element
of sorrowing, the element of equanimity, the element
of ignorance. When, Ananda, he knows and sees these
six elements, it is at this stage that it suffices to say,
'The monk is skilled in the elements.''

The Buddha then explained still other ways of being skilled in the elements and further on we read that Ananda asked again :

'Might there be another way also, revered sir,
according to which it suffices to say, 'The monk is
skilled in the elements'?'

'There might be, Ananda. There are these two
elements, Ananda: the element that is constructed and
the element that is unconstructed. When, Ananda, he
knows and sees these two elements, it is at this stage
that it suffices to say, 'The monk is skilled in the element. 

1.  When realities are classified as eighteen elements, what element 
is cetasika?
2.  Which paramattha dhammas are vinnana-dhatu
(consciousness-element)?
3.  Is mano-vinnana-dhatu (mind-consciousness-element) included
in vinnana-dhatu?
4.  Through how many doors does mano-dhatu experience an object? 
5.  Why is also nibbana an element?