But the West could not be conquered so easily. A new reaction of the West occurred.

The question was whether the one person, Jesus Christ, has one or two wills. One speaks in this time of monoteletis and duoteletis. They fought with each other, but finally this time the West prevails. Christ has two independent natures; the human nature is not swallowed up by the Divine.

You can grasp this development if you use the key of the problem of salvation and how salvation is related to the individual, to history, to personal life. Here the West was clear; the East was not.

The last fight in the east was about the icons.Ikon means image, the images in the churches of the Fathers and Saints. The icons deserve veneration and not adoration.

But if one asks what this actually means, we must say that in popular understanding veneration always develops into adoration. . . . This was perhaps for us not the greatest thing the East gave the West – although I would say that the salvation of human nature is something extremely great – but there is still something else in the East, namely the development of mysticism. To this we will go tomorrow by dealing with the classical early Christian mystic (ca. 500), Dionysius the Areopagite , who influenced everything in West and East after Chalcedon.
Paul Tillich, A History Of Christian Thought – Table of Contents