How is liberation achieved?

The Noble Truths are conditioned because they require the experienced world to be empty of Essence (the Truths would not hold in a world where an independent Self was perceived and directly knowable in the here and now). The path is conditioned as it is an Eightfold Path, requiring right view, right though etc. Nibbana is unconditioned, but when brought within the confines of thought or language it will be conceived as conditioned, because language and thought are conditioned experiences.

A subject's direct knowledge of the cessation of the 'sphere of neither perception nor non-perception', and that there is no thing further beyond that, does not fit into language very well if you wish to use the verb 'to perceive' with regards to what the subject is experiencing! Because this is the point at which all mental fermentations cease (whether perception or non-perception), the mental state is beyond designation, if being reasonable. I would say it is fair to say that it is unconditioned in the here and now of that individual. The process of arrival to it however, must be conditioned on previous meditative states. And because the mind that experiences direct knowledge is still conditioned by the body, there will be an exit from the perception of cessation. So yes, the experience of Nibbana is impermanent (as any and all experiences must be), the knowledge of it however can carry through beyond the experience, and remain 'permanently' with the Arahant until their parinibbana. (That's my thought, but I am still thinking it through to be honest!)

In Majjhima Nikaya 1 it is stressed that conceiving any thing beyond the direct knowledge of that thing (going beyond impermanence, suffering and non-Self, or not 'treating this as this and that as that' in short) is effectively wrong view. The direct knowledge of Nibbana must therefore be unconditioned, because only conceptual construction brings it down into the forum of the conditioned, and otherwise its 'being' and its 'perception' would not equate, which would be delusion for the subject of the perception.

https://aeon.co/essays/the-logic-of-buddhist-philosophy-goes-beyond-simple-truth is a very interesting article on the logic within the catuskoti that may provide some clearer information too!

"If the path leads to liberation then liberation should be conditioned and impermanent. But nirvana is beyond extremes so the path cannot lead to nirvana. How does it work then?"

This is the fundamental difference between Theravada Buddhism and Mahayana Buddhism.

As noted, that due to dependent origination, all changes are impermanent, hence there is no permanent cessation or attainments of any kind.

As the Heart Sutra stated:

There is no suffering, no accumulating, no extinction, no way, and no understanding and no attaining.

Without it seeming like some kind of crazy wisdom what it is saying is: Suffering is ultimately impermanent. Accumulation is ultimately impermanent. Cessation is ultimately impermanent. The Noble Eightfold Path is ultimately impermanent. Wisdom is ultimately impermanent. Attainments are ultimately impermanent.

Nirvana as cessation is relative to existence of suffering. The end of suffering is itself Nirvana. Both of them are impermanent.

This is the clarity of the Prajna Paramita which will cut through any metaphysical claims of Nibanna being a magical unconditioned deathless dimension, a birthless state of no further fabrications etc.

If Nirvana is permanent, the Buddha and his Arahants would never have to meditate ever again. Yet in all the scriptures they are seen to practice constantly even after the attainment of Arahantships.

This is why during the Early Buddhist Schisms, a big point of debate was made over whether Arahants could regress. Yes theoretically they could certainly regress if they stop all their Dharma practice. However, knowing this, a real Arahant with Superior Right view would never stop practicing the Noble Eightfold Path. And hence can end suffering indefinitely (but not permanently).

This is also why Mahayana move away from the four discrete stages of Enlightenments (Stream Entry, Once Returner, Non Returner, Arahantship) to one of continuous practice - a Bodhisattva.

If you pay attention to the description of the four stages of enlightenment, you will realize they describe the Threefold factor of the Eightfold Noble Path, namely Ethics, Concentration and Wisdom. Hence a stream enterer is one who has attained Right View and Right Intention to practice the Noble Eightfold Path. A once returner is one who has cultivated his ethics. A non returner is one who is accomplished in meditative concentration able to hold off lustful cravings indefinitely. And an Arahant is one who attained Superior Right View and Superior Right Intention with understanding of the causes and conditionality that gave rise to the afflictions in the first place and end them, attaining the end of suffering Nirvana. You can see similar descriptions of the Ten Oxherding pictures.

And he passes far beyond all confused imagination and reaches Ultimate Nirvana.

Of course the catch is that every step along the way is conditional and indeed reversible. There is no sabhava or permanent nature to any of these states. Hence no one could truly be said to have attained anything. This is why things are said to be Non-Dual in Mahayana, it is not that ignorance and wisdom are the same, but that they are both impermanent and cannot be permanently separated from each other.

no ignorance or ending of ignorance

So if everything is impermanent why practice Buddhism at all. Because it is useful! A person who does not practice will suffer indefinitely because of the cause and contions for mental afflictions are there. The Dharma is still a very useful medicine to treat your mental afflictions! A table is very much impermanent and having no essential 'table nature', but it is still very useful to put your things on.

I like the Brahmana Sutta (SN 51.15) which uses "going to a park" to illustrate it.

Incidentally (and I don't think this is the main point of the sutta) I think that "park" was the same word as used for "monastery", because in earliest times the monks were in parks rather than monasteries.

In much the same that water is wet regardless of whether you are swimming or standing on the beach, you still have to jump into the ocean to know for certain.

The meaning of nirvana being unconditioned is that nirvana does not arise due to causes and conditions. This is because nirvana is a negative phenomena, since it is the final true cessation.

However, we say that the achievement of nirvana is caused by path.

In the same way, the absence of John in the room is permanent and unconditioned. If John leaving the room caused the absence of John in the room, it would follow that John's absence would start a moment after John left, since a cause and its effect are not simultaneous.

Because we are in fact, in Nirvana, but we - don't know about it. Thus we are spending all our lives wandering around. The path is that finally one decided not to wander but taking a path one believed that's the right path to go home; going through this path from beginning to end we then be shown that in fact, we are actually all the time already in Nirvana. That's why the path should be abandoned at the end of the path; or sometimes the path is metaphorized as the boat ferrying one to the other side of the ocean. So... How does it work then? hmmmm... it's working like, a minus minus 1 will be a 1 {-(-1)=1}.

Or, following Tenzin Dorje's, it's like, "John is not home". However, to realize the fact for oneself, one must walk (The Path) from where he is back home, open the door, then, "Ooops, John is really not home!"

=====

§。Sequel。§

By sheer chance, this someone has the Mahayanist mind, thus the story continues:

He looks up the wall the portrait of John The Great staring back at him like Da Vinci's Mona Lisa the enigmatic smile. With disbelief slowing he turns to the mirror on the table, examining his face, "Goshhh... I'm John The Great!" He then once again reaches into his pocket re-took the key out, fondling it in his hand, musing, "Holy crap... all those years since I lost my mind I was wandering around in delusion, believing I'm John Lemon... "

§§§ 。。。balloons 。popcorns 。sob 。applause 。tears-snots-saliva 。 ...The End 。。。§§§

This Path is a process where the practitioner goes from the Conditioned to the Unconditioned. Stream Entry represents the point at which the gravitational pull of the 'Unconditioned' exerts a greater force than that of the 'Conditioned'. A Stream Entrant's practice is likely to be less affected by the conditions around them; this would depend upon an individual's propensities so, for example, someone who had a tendency to over-indulgence in food may become less bound by that desire even when delicious food is around, or someone who always became angry when contradicted may find it easier to hold their temper in check under that condition.

What follows after Stream Entry isn't merely the tidying up of a few loose ends, but rather undertaking the complete and radical overhaul of our ethical lives, of body, speech and mind, to the point of perfection. When viewed in this way, the attainment of Stream Entry begins to look like the beginning of the principal task of the spiritual life. The Once-Returner is no longer dominated by hatred or craving, that there are no longer any times in their lives when they are overwhelmed by such unskillful emotions. These emotions may arise occasionally in a weakened form, and only in the midst of awareness – they don't dominate.

When it comes to the next level, in addition to having broken the first three fetters and possessing an unshakeable faith in the Three Jewels, the Non-Returner has attained complete ethical purity. It's not that they don't conceal their unskilfulness, they just don't have any, whether of body, speech or mind. They are almost flawlessly motivated by generosity, love and wisdom.

The last five fetters remain of course, but these are exceptionally subtle in comparison to what has been broken in the fourth and fifth fetters. Also, because Non-Returners are not subject to any hindrances, the Eight Jhānas are readily accessible to them. There are examples of both monastic and lay Non-Returners in the Canon. There is the figure of Gatikāra the Potter, for example, who remains in the household life to care for his ageing parents, but he is an extraordinarily holy man.

Then there is the example in the householder Ugga of Vesālī (Anguttara Nikāya VIII,21) who had four young wives before he attained the state of Non-Returner, at which point he told them he could no longer remain their husband. So he asked them to choose between remaining in his house and “doing good deeds”, returning to their former families, or marrying another man of their choice. When his first wife said she wished to take another husband he gave her to the man she indicated, reporting that on doing so he felt no change of composure in his heart. This seems to imply that, although he had attained ethical perfection and equanimity on becoming a Non-Returner, prior to that, as a Once-Returner, he had still experienced craving and thus fell short of the highest ethical standards. This shows that going from the Conditioned to the Unconditioned is a process.