In the Buddhist world today, there is much discussion among meditators about the relevance of Jhana (to be explained below). The first question usually asked is "Must one achieve Jhana first to become fully Enlightened (Arahant), or is it possible to reach the Supreme Goal without any experience of Jhana?"
Those who ask this question are usually those who have not yet experienced Jhana themselves. It is difficult to do what is necessary to realise Jhana; so most people ask this question wanting to be told that Jhana is not essential. They want to be told that their inability is not an obstacle. They want a quick and easy way to Nibbana. Such people will be pleased and even inspired by a teacher who tells them what they wanted to hear anyway - that these Jhana states are unnecessary - and they will follow this teaching because it is convenient. Unfortunately, Truth is seldom convenient, and rarely agrees with what we want to hear.
On the other hand, a meditator who has familiarity with Jhanas will recognise them as blissful states of letting go, and it is right there, in the experience of letting go, letting go that the relevance of Jhana is known. The First Jhana is the natural result of letting go of the concern for sensory pleasure (Kama Sukha), by which is meant all concern, even for mere comfort, in the realm of the five external senses (sight, sound, smell, taste and touch). In the First Jhana, through sustained and complete removal of all interest in these five senses the meditator loses all sense of the body, and these five external senses disappear. They abide wholly in the sixth sense that is pure mind, and are still, in blissful inner silence. The Buddha called this "The Bliss of Renunciation", or the bliss of letting go. The Second Jhana is the natural result of abandoning a very subtle movement of attention towards and holding onto this blissful mind object. When this final 'wobbling' of attention is let go of, one experiences the even more pleasurable bliss of full inner stillness (Samadhi), where the mind is absolutely one -pointed and motionless. The Third Jhana is the natural result of letting go of the subtle excitement of rapture, and the Fourth Jhana is the natural result of letting go of happiness itself, so as to enjoy the most profound and immovable mental equanimity.
In Buddhism, experience, not speculation, and even less blind belief, is the criterion for understanding. A meditator simply does not realise what stillness, rapture, happiness or equanimity fully mean until they have become familiar with the Jhanas. But the experience of the Jhanas, these stages of letting go, give one direct understanding through experience of these mental phenomena, in particular happiness (Sukha) and suffering (Dukkha).
It is similar to the tadpole who has spent her whole life in the water but who can have no understanding of water because she has known nothing else. Then, when she grows up into a frog, lets go of the water, and attains to dry land, she knows both the nature of water and the way to go beyond it. In this simile, the water stands for Dukkha, the dry land for Jhana (not Nibbana - the frog still carries a little water on her skin upon dry land!), and the way to go beyond stands for letting go.
In this way, the practice of Jhana reveals the Path to fully ending Dukkha. The meditator who achieves Jhana will eventually ask "Why are these Jhanas so profoundly blissful? They will discover for themselves the obvious answer -"Because they are stages of letting go of that which they now see as fine forms of suffering!" When one is familiar with Jhana, and realises the origin of the bliss therein, one will come to see for oneself that all worldly pleasures, that is, of the five external senses (which include sexuality), are merely Dukkha. The attachment to the body and its sensory adventures will begin to fade away. One will understand clearly why all Enlightened Ones are celibate. Then, as one progresses onwards to the higher Jhanas and contemplates why each further one is ever more pleasing, one comes to understand that it is because one is letting go of refined mental attachments, such as the attachment to rapture, happiness and equanimity. It becomes clear that even these most lofty of mind states are just refined forms of suffering, because when one lets them go, then more suffering goes too. The higher one goes , the more Dukkha is let go of and through this process Dukkha becomes known. One cannot know fully the Truth of Suffering, and thus the Buddha's Four Noble Truths, except by letting go of suffering through the experience of Jhana.
It is very odd, therefore, that some suggest that the practise of Jhana leads to attachment. How can, what is the practice of letting go, lead to attachment? Indeed, the Buddha repeatedly said that these Jhanas should not be feared, but should be developed, and that when these Jhanas are indulged in regularly they lead to Sotapanna, Sakadagami, Anagami, and Arahant, the four stages of Enlightenment. (See the Pasadika Sutta of the Digha Nikaya).
Once Full Enlightenment is reached and all attachments are removed, then letting go into Jhana becomes as natural as a leaf released from a tree falling downwards to the ground. Indeed, one's present ability to let go and experience the Jhana is a measure of one's true understanding of the Dhamma and consequent lack of attachment. Ajahn Brahmavamso BSWA Newsletter, Mar/Jun 1997. Source: www.what-buddha-taught.net