What we have written about the nature of evil thoughts also shows their causes. According to St. Gregory of Sinai, the origin and cause of evil thoughts lies in "the splitting up, through man's transgression, of his single and simple memory" (398). Before his transgression man's memory was simple, that is, it had no passion and it was turned entirely towards God. All the powers of the soul were centred on God. Immediately after the transgression this single memory was split up. St. Thalassios teaches that evil thoughts arise from three sources: the senses, the memory, and the body's temperament. The worst are those that come from the memory (399).