The Buddhism of the Pali Nikayas and certainly Zen Buddhism dwell on the unconditioned through its various synonyms. It's opposite, the conditioned, describes not only our world but the psychophysical organism we inhabit and wrongly take for a refuge. To be specific, the Five Aggregates (P., khandhas; S., skandhas) are conditioned and, by implication, the self or ātman is unconditioned since the Buddha teaches that our self is not anyone of the aggregates which are conditioned. On this same track, to realize nirvana means to see our self which is beyond the covering of the conditioned. Here in the Samyutta-Nikaya (S. iv. 369) we find an apt description of the taintless (anāsavaṃ) which can apply to nirvana, the mind and ourself (sayaṃ).
"The unconditioned, the end, the effluent-less, the true, the beyond, the subtle, the very-hard-to-see, the ageless, permanence, the undecaying, the featureless, the undifferentiated, peace, the deathless, the exquisite, bliss, solace, the exhaustion of craving, the wonderful, the marvelous, the secure, security, nirvana, the unafflicted, the passionless, the pure, release, non-attachment, the island, shelter, harbour, refuge, the ultimate."
In Zen Buddhism our goal is to see our true nature, this seeing being kensho which is just another way of saying we've, personally, realized the unconditioned. The path leading to the unconditioned is not, in essence, unlike the path described in the Pali Nikayas which is signless being absent of any trace of the conditioned including the born, the become, the made, etc. We should note that our journey to truth is not pathless, far from it. There is a path but it is a path not dependent on signs being ultimately void of the conditioned. From Zen's angle, when Mind is completely—all-at-once stilled—we behold the unconditioned aspect of Mind. To reach this aspect of Mind is rightly nirvana. It is permanent, without suffering and ātman (Buddha-nature).
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