The notion of progress is a modern invention. It is also — and this explains its unthinkableness by our orthodox ancestors — a heretical notion. For an orthodox medieval churchman there could be no such thing as progress. Man had been created complete and fully human. There was no question of his developing or growing up. Human nature was changeless and had remained so from the beginning. Circumstances might vary from place to place and from epoch to epoch; but this variation was the merest accident. Beneath the shifting surface, human nature remained substantially the same.
The doctrine of progress was made possible by the decay of Christian orthodoxy.