It was only when something had happened, not Once Upon a Time, but to a specific group of people living in a real place during the reign of a Roman bureaucrat that creeds became necessary, because real memories, not dreams and legends, were involved. For this people was constantly being pressured by its neighbours and by its own sinful tendencies to forget what had happened–to remove Jesus to Cloud Cuckoo Land where anything and everything might be said of him, to make him more amenable to pagan tales and dreams. That is why John has to tell his flock:
Beloved, do not believe every spirit, but test the spirits to see whether they are of God; for many false prophets have gone out into the world. By this you know the Spirit of God: every spirit which confesses that Jesus Christ has come in the flesh is of God, and every spirit which does not confess Jesus is not of God. (1 Jn 4:1–3)
Jesus Christ–God–has come in the flesh. More than this, he has been raised in the flesh too: breaking bread, eating fish, being touched after his Resurrection. And still more than this he has pressed into the minds, hearts, mouths, and hands of his disciples a Eucharist of that crucified, raised, and glorified flesh with the word, “Do this in memory of me” (Luke 22:19; 1 Corinthians 11:24-25). He has refused to stay in the realm of myth and has left footprints and drunk water from a well in Nazareth that can be located with a GPS. He is not merely the comfortably abstract “that which was from the beginning”.
He is, far more alarmingly, that “which we have heard, which we have seen with our eyes, which we have looked upon and touched with our hands” (1 John 1:1). And so, the Church’s history necessarily became one long and careful act of remembering, not imagining—designed to make sure that their past was not lost. Since what had happened was so strange—and so fraught with the possibility of being misunderstood in a thousand ways—the early Christians therefore were immediately committed to creating Creeds: summaries of their experience that, while initially brief (“Jesus is Lord” (Romans 10:9)), expanded in length over time to make sure that the broad contours of the basic story and its meaning were not lost.