The school of moralists responsible for the doctrine of the Fall of Man has been obliged to assume the existence in creation of a personal Devil as the counterpart of a personal God. They portray God as the embodiment of all that is good, and the Devil as the embodiment of all that is evil. They claim that God created man in His own image and found him to be perfect. In the beautiful poetical allegory of Genesis the world is represented as a garden in which everything is perfect; and the man and woman whom God created are placed there for happiness. The beginning of their unhappiness is attributed to the subtlety of reason, personified in the serpent, which suggests that the perfect creature of God would be made more perfect by a knowledge of good and evil. God's measurement of values was provided by the ever-present capacity of the human body to differentiate between pleasure and pain.