From the Cūḷavedalla Sutta:
Is the Path Conditioned or Unconditioned?
“Ariyo panāyye, aṭṭhaṅgiko maggo saṅkhato udāhu asaṅkhato”ti?
“Is the Eightfold Path conditioned or is it unconditioned?”
The Path Is Conditioned
To this question, Dhammadinnā gave the following answer:
“Ariyo kho, āvuso Visākha, aṭṭhaṅgiko maggo saṅkhato”ti.
“Friend Visākha, the Eightfold Path is conditioned.”
The Eightfold Path is conditioned and proceeds from causes, such as insight. Only nibbāna is unconditioned. This nibbāna symbolises supreme bliss and tranquillity because the faculty of the Noble Path gives no chance for the occurrence of defilements. Tranquillity, not being an occurrence, cannot be said to have arisen from a cause. What is meant by this nibbāna is that no new existence comprising unsatisfactory mind and matter will arise, because defilements, which are its cause, have become extinct, thereby bringing forth a blissful state of freedom from all forms of craving and human passion. This also cannot be called the cause of conditioned phenomena since there is no incidence or occurrence. It should only be regarded as the unconditioned, the unmade, which is not produced.”
From the Milindapañha —
The Uncaused
“Nāgasena, there are things in the world that have come into existence through kamma, others are the result of a cause, and others are produced by season. Tell me, is there anything that does not fall into either of these three categories?”
“There are two such things, O king; space and nibbāna.”
“Do not, Venerable Nāgasena, corrupt the words of the Conqueror, or answer a question without knowing what you are saying!”
“What have I said, O king, that you speak to me thus?”
“Venerable sir, it is right what you say about space but with hundreds of reasons did the Blessed One proclaim to his disciples the way to the realisation of nibbāna and yet you say that nibbāna is not the result of any cause.”
“It is true, O king, that in many ways did the Blessed One point out a way to the realisation of nibbāna, but he did not point out a cause for the arising of nibbāna.”
“Here, Nāgasena, we go from darkness to greater darkness; from uncertainty to utter confusion. If there is a father of a child we would expect to find a father of the father. Just so, if there is a cause for the realisation of nibbāna we would expect to find a cause for its arising.”
“Nibbāna, O king, is unconstructed, therefore no cause has been pointed out for its production. It cannot be said of nibbāna that it has arisen or can arise; that it is past, present, or future; or cognizable by the eye, ear, nose, tongue, or body.”
“Then, Nāgasena, nibbāna is a condition that does not exist!”
“Nibbāna does exist, O king, and can be cognized by the mind. A noble disciple whose mind is pure, lofty, sincere, unobstructed and free from craving can attain nibbāna.”
“Then explain by means of similes what nibbāna is.”
“Is there such a thing as the wind?”
“Yes there is.”
“Then explain by means of similes what the wind is.”
“It is not possible to explain what the wind is by means of similes but it exists all the same.”
“Just so, O king, nibbāna exists but it is impossible to describe.”