Jhāna means absorption in Pali. This is the state where one develops a type of concentration that is called appanā samadhi, or absorption concentration. During this state of concentration, there is a complete but temporary elimination of fivefold sense-activity and the five hindrances.
Why do we practice jhāna? The reason for practicing jhāna is to develop concentration. Buddha said that "a person whose mind is concentrated knows and sees things as they actually are” (AN 11.2, Cētanākaranīyasutta). This means to see the ultimate reality, that is, the paramattha dhamma, one should develop concentration. Then which type of concentration should we cultivate? Buddha explained in the Mahasatipatthana Sutta what right concentration is: it is the development of the first, second, third and fourth jhāna. These four types of jhāna are called the 'rupa-vacara jhāna'.
Therefore, we should understand that to develop 'right concentration' (samma-samādhi) of the noble eightfold path, then we should develop jhāna concentration. In the seven stages of purification stated in the Visuddhimagga, the development of concentration is referred to as purification of mind, called 'cittavisuddhi'. This purification of mind serves as the foundation (after sīla: morality) for later vipassana knowledge to come as a concentrated mind 'can see things as they really are'. As everyone knows that the objects of contemplation for vipassana are the nāma (mentality) and rūpa (materiality). So to see the nāmarūpa in their ultimate reality form, our minds need to be concentrated and the type of concentration we develop should be the way Buddha expounded: not contemporary, modern and self-made methods. Buddha said in the Maha-satipatthana Sutta that the noble eightfold path is the only way towards purification and liberation. So, if you are someone who wants to liberate from rounds of rebirth, purify yourself of defilements and attain Nibbāna, you must follow the one and only path laid out by Buddha.
So how we do we achieve jhāna? Buddha laid out forty sāmatha objects that a practitioner can use to achieve concentration.
- 10 totalities or devices (kasina)
- 10 kinds of foulness (asubha)
- 10 recollections (anussati)
- 4 divine abidings: the Brahmavihara of Metta, Karuna, Mudita, Upekkha
- 4 immaterial states (arūpa: formless jhāna)
- Repulsiveness of nutriment (ahare-paṭikula-sañña): loathsomeness of food.
- Reflection on the four elements
Among these forty meditation objects, a meditator can achieve jhāna through thirty meditation objects. To name a few, they are ānapāna, metta, 10 kasina, asubha, and 32 body parts. The other ten objects can help meditator achieve near-jhāna concentration called the access concentration or upacara-samādhi. One might question then, is access concentration or upacara-samādhi also 'right concentration'? The answer is yes and this is mentioned in the Visudhimagga: both access concentration and eight attainments are called purification of mind (cittavisuddhi). Although Buddha said in the Mahasatipatthana Sutta that the achievement of 'right concentration' (samma-samādhi) of the noble eightfold path means the development of the four jhāna, this is further elaborated in the commentaries using the analogy of 'picking up a snake from the middle.' In this analogy, if you grasp a snake from its midsection, you can simultaneously see and understand its head, body, and tail. Similarly, by exclusively discussing the four jhānas (the body), one can infer that 'right concentration' encompasses access concentration (the head), the four rūpa jhānas (first to fourth: the body), and the four arūpa jhānas (fifth to eighth: the tail). Since the first jhāna can only be attained after achieving access concentration, the latter can be regarded as a manifestation of 'right concentration.' Moreover, one may train themselves to develop up till the eighth jhāna, called 'arupa-vacara jhāna', too to achieve 'right concentration'. To summarise, the access concentration, four rūpa and four arūpa jhāna are called 'right concentration'.
Then how are these two different? Jhāna concentration is far more superior and powerful than access concentration so one can expect to 'know and see things as they actually are' in a more profound manner. These jhāna are also the basis of further concentration-based attainments: the 'abiññā'. They are the mundane (lokiya) powers attainable through the utmost perfection in concentration (samādhi). They are: magical/transformation powers (iddhi-vidha), divine ear (dibba-sōta), penetration of the minds of others (cetō-pariya-ñāna), remembrance of former existences (pubbe-nivāsānussati), and divine eye (dibba-cakkhu). [Please note that the guidance given for jhāna is NOT for such attainments at this stage but rather to gain concentration for further vipassana discernment only].
It is very crucial NOT to skip the development of concentration because a person whose mind is not concentrated will not see the ultimate reality (paramattha) nature of mentality and materiality (nāmarūpa). If one were to say, access or absorption concentration is not required, samādhi is not required or one were to skip concentration practice altogether entirely in favour of vipassāna, it would be considered Adhamma: a false doctrine that contradicts the teachings of the Buddha and the noble eightfold path. Therefore, if you are one who wishes to liberate from suffering, then you must follow what Buddha taught and cultivate "right concentration" by following the noble eightfold path exclusively.
May you realise the four noble truths in this lifetime.