There are two types of pervasion:

I. Unspecified pervasion (anodhiso pharana)
II. Specified pervasion (odhiso pharana)

UNSPECIFIED PERVASION
In the texts the unspecified pervasion of metta is metta given to beings not of any specified types. They are:

1. sabbe satta – all beings (sentient beings with feelings)
2. sabbe pana – all living things (beings that breathe and live)
3. sabbe bhuta – all creatures (beings that arise owing to their kamma)
4. sabbe puggala – all individuals (beings seen as individuals)
5. sabbe attabhavapariyapanna – all personalities (beings with personalities)

These five actually convey the same meaning – i.e. beings. However, different words are used. It helps to break the monotony, increase perception and hence concentration.

Unspecified pervasion is usually done more successfully (i.e. with mastery of absorptions, etc.), only when the sending of metta to individuals, such as the lovable being, as an object has first been done. Firstly this is because it is easier to develop concentration on an individual. We can understand this when we look into the more extended nature of the unspecified object. Hence a tendency to disperse the concentration. It is as if a light to be spread out over a wider space has to be brighter. It will not be necessary if just access concentration is required.

Secondly when we say "all" we really mean to include the hostile ones, otherwise deep inside we may mean "all except"...

Definitely one cannot visualise all beings. One has only to bear in mind just what it means. It is as if one does not have any object, only the metta for all beings is developed. As concentration deepens one cannot help but notice that it often occurs in an expanded nature, and is very light and blissful.

One needs to go through the four aspirations with respect to the five "unspecified" objects repeatedly:

1. May all beings be free from enmity/danger.
Sabbe satta avera hontu

2. May all beings be free from mental suffering.
Sabbe satta abyapajja hontu

3. May all beings be free from physical suffering.
Sabbe satta anigha hontu

4. May all beings take care of themselves happily.
Sabbe satta sukhi attanam pariharantu

May all living things... may all creatures... may all individuals... may all personalities...

One does this until absorptions have been reached and mastered.

Unspecified pervasion of metta enables us to develop a universal type of metta. It makes us give metta equally to each and every being without giving more to anyone. Hence it is universal, flexible, versatile and stable. It can therefore help to enhance our ability to communicate and see to the needs of all groups as a whole, hence executing impartial decisions beneficial to all. "Happy is the one who bears no ill-will to any living creature."

For one who has thoroughly developed this state of mind, one will truly experience ecstatic happiness.

SPECIFIED PERVASION
In the case of specified pervasion, the groups are well defined. It is true that each of us may bear certain preferences for or grudges against different groups of people. Hence our relationships to them differ. It also implies that the metta given to each group can be unique in its own way with respect to attitude, expression, satisfaction of needs etc. Their effects and benefits as we will see also differ.
In tradition, we have 7 such groups but these can be seen to come from 3, as each of these 3 groups would cover all if not most of the beings.

They are as follows:

GROUP A
Sabbe itthiya – all female kind.
Sabbe purisa – all male kind.

Metta to the opposite sex can be more freely done if done in groups as it is less likely to develop strong attachment to anyone.

As there are possibly some men-haters or women-haters, it should do them good to remove such hatred. Then there may be the other extreme who should learn more with regards to unselfish love. All these show that the healthy, pure metta relationship has to be learned. Ability to give metta to them equally well is the real way to effect a truly female – or for that matter male – liberation.
There the 4 aspirations are made first to the female kind and then to the male kind to gain the levels of concentration, mastery, and so forth.

GROUP B
Sabbe ariya – all nobles

i.e. the community which comprises those who have experienced any of the 4 stages of attainment (stream winner, once-returner, non-returner and arahatta.)

Sabbe anariya – all the beings of the world outside the previous group (i.e. nobles).

It is obvious that the first group would be easier to give metta to than the second group. Then there is also metta to be developed within the 2 groups.

Obviously it builds up a healthy relationship between people striving for peace. It instils metta and cohesiveness within the spiritual community, smoothing it, fixing it and builds it up into a potent force that spreads to others outside as described in anariya.

For the more advanced, compassion would tend to arise and for the slower, respect, a form of sympathetic joy. When we make sure we are developing metta, we instil something more – friendliness. Otherwise the distance may be too wide for effective communication, and metta can help bridge the gap.

Hence we radiate metta to them with the same 4 aspirations to gain the respective absorptions and mastery.

GROUP C

Sabbe deva – all deities,
i.e. celestial beings of devas and brahmas.
Sabbe manussa – all humankind.
Sabbe vinipatika – all unhappy states,
i.e. those of the woeful realms of animals, petas, asuras, and hell beings.

What impresses us here is that the group barriers posed by different realms of existence can be removed when it comes to metta. Advantages such as "devas protect him" speak for themselves. We also have forest monks with metta who live among wild animals such as tigers. The first step for effectiveness is the recognition that there are such worlds and beings. The second step is metta and not fear, for as the saying goes – what they fear, they hate. The third step is to see the blessings of metta and disadvantages of anger.

The motivation should drive us on to practise metta to deep concentration using the method as described for the others.

It is obvious that when we give metta to deities who enjoy more sensual happiness, the metta may shade into sympathetic joy and to the suffering beings shade into compassion. With humans we see the human fellowship and so what is radiated becomes more distinctly metta. However if we can look with understanding that all these are beings who may be our friends in this or past lives, then a tone of friendship metta can be aroused.

Unspecified pervasion can be done to all the 7 groups, one after another with the 4 aspirations to gain the concentration. It allows us to give very strong metta to specific groups of beings in their context:

1. Sabbe itthiyo: May all female kind.
2. Sabbe purisa: May all male kind.
3. Sabbe ariya: May all nobles.
4. Sabbe anariya: May all worldlings.
5. Sabbe deva: May all deities.
6. Sabbe manussa: May all humans.
7. Sabbe vinipatika: May all unhappy states

If we wish, we may even expand further to the different races, different religions, all age groups and those in different habitats, etc. In Malaysia – where multi-cultural differences occur, it ought to be a regular practice. In the Karaniyametta Sutta we can see some of these mentioned: whatever beings that exist:

1. weak or strong without exceptions.
2. long, big, short, tiny, medium-sized, bulky, small.
3. seen and not seen.
4. near and far.
5. those who are to come into existence.
6. those who have come into existence.
7. those who do not seek rebirth.

The division is countless.

Each as we see will help to overcome anger that causes that particular social malady and bring about the benefits.