In a very interesting dialogue between Milinda and Nâgasena, communicated by Mr. Spence Hardy, Nirvâna is represented as something which has no antecedent cause, no qualities, no locality. It is something of which the utmost we may assert is, that it is:
Nâgasena. Can a man, by his natural strength, go from the city of Sâgal to the forest of Himâla?
Milinda. Yes.
Nâgasena. But could any man, by his natural strength, bring the forest of Himâla to this city of Sâgal?
Milinda. No.
Nâgasena. In like manner, though the fruition of the paths may cause the accomplishment of Nirvâna, no cause by which Nirvâna is produced can be declared. The path that leads to Nirvâna may be pointed out, but not any cause for its production. Why? because that which constitutes Nirvâna is beyond all computation,—a mystery, not to be understood.... It cannot be said that it is produced, nor that it is not produced; that it is past or future or present. Nor can it be said that it is the seeing of the eye, or the hearing of the ear, or the smelling of the nose, or the tasting of the tongue, or the feeling of the body.
Milinda. Then you speak of a thing that is not; you merely say that Nirvâna is Nirvâna;—therefore there is no Nirvâna.
Nâgasena. Great king, Nirvâna is.
Another question also, whether Nirvâna is something different from the beings that enter into it, has been asked by the Buddhists themselves: