A common problem that people have with both the Father, Son and Holy Spirit, God (Trinitarian Theology) and with the dual natures of Christ (Christology) is the very simple idea of maths. 1+1+1=1 or 1+1=1, how does that work, it doesn't (short of trippy, funky maths which, aside from being beyond my understanding, is really rather beside the point).
But, it's not supposed to work based on our logic.
"If God were small enough to fit in our heads, He would not be big enough to worship" - Paul Tyson, c.2001.We have to be willing to admit that God is bigger than us, that in the same way as we can look at the world around us and comprehend it without it comprehending us, God comprehends us without us comprehending it. In fact, moreso - God created us, so the relationship is not dissimiliar to God knowing us like an engineer knows their building, or a watchmaker knows their watch, or a programmer knows their program.
And, back to the point...
"certum est, quia impossibile / it is certain--because it is impossible." - Tertullian, 2nd Century ADHow could humans come up with something like Trinitarian theology? It's a mess, and on quite a number of levels nigh-on impossible to defend - it took the Church until the late 300s to have the final church-wide (i.e. second ecumenical) council on Trinitarian theology, and until the 600s to have the final Church-wide (i.e. sixth ecumenical) council on the subject of Christology.
But, the point is that we didn't come up with it. If humans had, then humans would feel quite free to change it - and many did try. Rather:
"We cannot change these things, because we did not make them. They came from above." - Abp Stylianos of Australia, 2002.Because the Trinity was revealed to us, because the two natures of Christ are so blatantly revealed to us, we do not have the luxury of changing them so that we get better advantage in a debate, nor the luxury of changing to a more defensible position. We must be true to what we have seen and beheld, not to what we can logically defend.
And so, we believe the logically impossible - or rather, we see the limits of human logic and human intelligence. At some point we must realise that we can't go further - our brains aren't big enough, we aren't ready, we're not quite 'solid' enough (which seems to convey the general idea) - and we must simply bow before the mystery.