I have heard that on one occasion Ven. Ananda was staying in Kosambi, at Ghosita's Park. Then the Brahman Unnabha went to where Ven. Ananda was staying and on arrival greeted him courteously. After an exchange of friendly greetings & courtesies, he sat to one side. As he was sitting there, he said to Ven. Ananda: "Master Ananda, what is the aim of this holy life lived under the contemplative Gotama?"
"Brahman, the holy life is lived under the Blessed One with the aim of abandoning desire."
"Is there a path, is there a practice, for the abandoning of that desire?"
"Yes, there is a path, there is a practice, for the abandoning of that desire."
"What is the path, the practice, for the abandoning of that desire?"
"Brahman, there is the case where a monk develops the base of power endowed with concentration founded on desire & the fabrications of exertion. He develops the base of power endowed with concentration founded on persistence... concentration founded on intent... concentration founded on discrimination & the fabrications of exertion. This, Brahman, is the path, this is the practice for the abandoning of that desire."
"If that's so, Master Ananda, then it's an endless path, and not one with an end, for it's impossible that one could abandon desire by means of desire."
"In that case, brahman, let me question you on this matter. Answer as you see fit. What do you think: Didn't you first have desire, thinking, 'I'll go to the park,' and then when you reached the park, wasn't that particular desire allayed?"
[see continuation:
http://www.accesstoinsight.org/tipitaka/sn/sn51/sn51.015.than.html]