This week, I have been studying about John Cassian, a monk/priest who lived in the fourth century (360-433). His two most famous works are the Institutes and the Conferences. In the latter, he records conversations with some of the more famous monks who had fled to the deserts of Egypt when Christianity was made the official religion of the empire by Constantine. I was especially encouraged by these words from his conference with Abba Moses, where they discuss the trouble of wandering thoughts and the challenge to fix the mind on God. Since thought life is one of my most difficult daily battles, I was totally blessed by these words from a man of faith from whom over 1,500 years separates me, but with whom I am connected as a fellow disciple of Christ.
"This movement of the heart is not unsuitably illustrated by the comparison of a mill wheel, which the headlong rush of water whirls round with revolving impetus. It can never stop its work so long as it is driven round by the action of the water. But it is in the power of the man who directs it to decide whether he will have wheat or barley or darnel ground by it. Whatever the man in charge of the business puts into it certainly must be crushed by it. So then the mind also through the trials of the present life is driven about by the torrents of temptations pouring in upon it from all sides and cannot be freed from the flow of thoughts. But it will provide the character of the thoughts that it should either throw off or admit for itself by the efforts of its own earnestness and diligence. If, as we said, we constantly return to mediation on the Holy Scriptures and raise our memory toward the recollection of spiritual things and the desire of perfection and the hope of future bliss, spiritual thoughts are sure to rise from this and cause the mind to dwell on those things on which we have been meditating. But if we are overcome by sloth or carelessness and spend our time in idle gossip or are entangled in the cares of this world and unnecessary anxieties, the result will be that a sort of species of tares will spring up and afford an injurious occupation for our hearts, and as our Lord and Savior says, “where the treasure” of your works or purpose “is, there your heart” is sure to be also."
(From Cassian’s Conferences: Conference I, Chapters 15-18)