How can God know Himself?

[Kreuzritter]

"Hypostasis" can also be translated as "Person," which means something similar but different than "Prosopon."

It can't be in the modern English sense of person.

One can see there's good reason that, despite popular use, the dogmatic definition of the Trinity didn't end up using the word prosopon. In Greek, being a mask and theatrical character, it has modalist implications; contrariwise, its cognate in modern English it has tritheist implications. In my experience most Christians these days seem to believe God is three "personalities" like three distinct and separate centers of consciousness that would have more accurately announced to Moses at the burning bush "We are" - if ones believes this, one is a tritheist, however one chooses to play with words like "one nature" to pretend one doesn't. At least the modalist maintains the subjective unity of God as "I am", while the former doesn't get anything right. In fact the line between the truth and modalism is far finer than that with tritheism. The difference is that an hypostasis is a concrete reality as and in which God necessarily exists, not a mere virtual appearance or set of accidents attached to an essence.