"As we know, there are known knowns.Lord Buddha said; " The subject of universe is infinite and only a Buddha can understand"
There are things we know we know.
We also know there are known unknowns.
That is to say we know there are
some things we do not know.
But there are also unknown unknowns,
the ones we don't know we don't know."
With unknown unknowns this is very true.