Observing through everything, all truth is in the observed.
Observing through a mirror, all truth is in the observer, and in what they are not, and they are complementary and they are the same.
Observing through a one-sided mirror, two people see the same truth differently, and they are compatible, and they are not the same.
Observing through a one-sided wall, two people see different truths similarly, and they are not compatible, and they are the same.
Observing through eachother, all truth is in the observers, and in what they are not, and they are complementary, and they are the same.
Observing through nothing, all truth is in the observer.