The neither-thought-nor-no-thought concentration. A state of meditation where there are no objects （concepts） yet there is no non-presence of objects. This is the highest state of the formless realm， and thus the highest existence of the three realms. It is not yet nirva^na， because there is still a very subtle kind of thought remaining. It is the fourth heaven of the four heaven of the formless realm 四无色， the most subtle state of the three realms.