That which is seen cannot be that which sees. The knife cannot cut itself.
In our language "That which is seen cannot be that which sees" But is this true? To say it is, presupposes that things exist, and are apart and separate from other things that exist.
If it is not true, then that which sees can indeed see itself the seer (perhaps with the aid of a reflective surface?)
My point being that when we get to this level, are we going to make our arguments using the words that we have already admitted, no longer have the ability to hold the meanings we are attempting to convey.
And herein lies my point that there is not one thing.