But it should also be said that Scripture does not ask us to believe in a contradiction. A contradiction would be “There is one God and there is not one God,” or “God is three persons and God is not three persons,” or even (which is similar to the previous statement) “God is three persons and God is one person.” But to say that “God is three persons and there is one God” is not a contradiction. It is something we do not understand, and it is therefore a mystery or a paradox, but that should not trouble us as long as the different aspects of the mystery are clearly taught by Scripture, for as long as we are finite creatures and not omniscient deity, there will always (for all eternity) be things that we do not fully understand.
Wayne Grudem