St. Isaac the Syrian on what happens "When knowledge follows the desire of the flesh"

"When knowledge follows the desire of the flesh, it brings with it these tendencies: wealth, vanity, adornment, rest for the body, and eagerness for the wisdom of that logic which is suitable for the administration of this world; it is constantly making new discoveries both in skills and in knowledge, and abounds also in everything else that is the crown of the body in this visible world. As a result of this, it comes to oppose faith . . . for it is stripped of any concern for God, and makes the mind irrational and powerless, because it is dominated by the body. Its concern is wholly confined to this world . . . It thinks that everything is in its own care, following those who say that the visible world is not subject to any direction. Yet it is unable to escape from continuing concern and fear for the body. So faintheartedness and sorrow and despair take hold of it . . . and worry about illnesses, and concerns about wants and lack of necessities, and fear of death . . . For it does not know how to cast its care onto God, in the assurance of faith in Him. It therefore engages in contrivances and trickery in all its affairs. When its contrivances are ineffectual for some reason, it does not see the secret providence, and fights the people who are obstructing and opposing it".

St. Isaac the Syrian, Mystic treatises 6, pp. 256-257, as quoted by Christos Yannaras in "The ethos of liturgical art," chap. 12 of The freedom of morality, trans. Elizabeth Briere, Contemporary Greek theologians 3 (Crestwood, NY: St. Vladimir's Seminary Press, 1984), 236n2.