Brian, certainly Christ existed prior to the creation and Aberaham, or that's what we beleivers believe.
Yes indeed, but as there were no Christians before Jesus' appearance then it would not be a Christian principle.
But really the principle could arguably be known to the prophets in the Old Testament, or to Moses, for example, and thus being a very old Christian principle, it could be a very old Jewish principle prior to that.
So, it is a very old Jewish principle that Christians took on after the death of Jesus?
Brian.