The demon of acedia — also called the noonday demon — is the one that causes the most serious trouble of all. He presses his attack upon the monk about the fourth hour and besieges the soul until the eighth hour. First of all he makes it seem that the sun barely moves, if at all, and that the day is fifty hours long. Then he constrains the monk to look constantly out the windows, to walk outside the cell, to gaze carefully at the sun.