I can thank Donald Rumsfeld for the term "known unknowns." Indeed, there are known unknowns. That much I know, though I can never show it to you.
But think about this. Thoughts come as perceptions. They are perceived.
The perceiver cannot be found. Whatever is located when searching is only another object of thought. Perception remains, out of reach as that which is aware of the search and the thought object.
To establish a model for discussion, consider this. We cannot see black holes but we can see the gravitational lensing they cause around astronomical objects. Black holes are inferred phenomena.
