Considered with respect to truth as disclosedness, concealment is then un-disclosedness and accordingly the un-truth that is most proper to the essence of truth. The concealment of beings as a whole does not first show up subsequently as a consequence of the fact that knowledge of beings is always fragmentary. The concealment of beings as a whole, un-truth proper, is older than every openedness of this or that being. It is older even than letting-be itself, which in disclosing already holds concealed and comports itself toward concealing.

P. 148

As old as the Jurassic?