For myself the fact that things like salvation, and faith & deeds can't be explained and grasped with a clear concise explanation, is a picture of how other than us God is. He is other than us, in size, in understanding, in love, in grace, in mercy..etc. etc.. He is something so far beyond our comprehension that the little bit we do grasp is but a grain of sand. (but what a precious grain it is)
So it makes sense that we grapple with things that are from God. I think as we work things like this out in our head, God will point us to Himself, to His Son and the cross, and say "There is your answer."

While understanding our faith/doctrine/theology is important, there comes a point where I just have to smile and point to my Mighty God, who calls me friend and say..."There's your answer."