John Cassian: “this most sublime tower of the spirit”

“…it is pointless… simply to talk about prayer, simply to direct attention to its ultimate reality, with its presupposition of the practice of all the virtues. The first task is to look at the succession of obstacles to be overcome and then to examine the necessary preliminaries to success. With the gospel parable for a guide, one must carefully calculate and gather together everything required for the construction of this most sublime tower of the spirit. And preliminary work will be necessary if the assembled materials are to be of any use, for they will not be able to support the sublime reality of perfection unless we unload all our vices and rid our souls of the wreck and rubble of passions. Then simplicity and humility must be laid as sure foundations on… the living earth of our hearts, on that rock of which Scripture speaks. There the tower to be built with our virtues may rest unshakably and rise with utter assurance to the heights of the skies. That tower resting on such foundations will not crumble, will feel no shock even when the mighty torrents of passion come pouring against it, when the raging tides of persecution are like a battering ram against its walls, when the cruel hurricane of storming devils pounds and thunders against it.”
St. John Cassian