Sometimes people say that Nirvikalpa Samadhi is a state where there is no knower and known. That is really a half-truth. To capture the essence of Nirvikalpa Samadhi, it is better to say that in Nirvikalpa the KNOWER and the KNOWN are IDENTICAL. It is only pure consciousness that by which its very nature is self-revealing and self-knowing.
Nirvikalpa in Sanskrit means “without thought or doubt or mental modification”. It is the absence of mental modification and presence of fullness of consciousness in Nirvikalpa Samadhi which allows for the clear recognition of the Self.
Self is both the Knower and the Known, the Seer and the Seen, without any duality. Self, being one without a second, is always self-knowing. There is no “other” for it to know. That is why we refer to the Self as Nirvikalpa. The reference to Nirvikalpa implies the nondual nature of the Self.