John Cassian

“It is inevitable that the mind which does not have a place to turn to or any stable base will undergo change from hour to hour and from minute to minute due to the variety of its distractions, and by the things that come to it from outside it will be continually transformed into whatever occurs to it at any given moment.”

“Wherefore a monk's whole attention should thus be fixed on one point, and the rise and circle of all his thoughts be vigorously restricted to it; viz., to the recollection of God, as when a man, who is anxious to raise on high a vault of a round arch, must constantly draw a line round from its exact centre, and in accordance with the sure standard it gives discover by the laws of building all the evenness and roundness required....”