"Now, if you want to drive away a wicked thought or desire, just grasp this little piece of advice I am going to give you, and stick to it.
"Do not argue with perverse thoughts or evil desires, but when they attack you, occupy your mind vigorously with some profitable plan or meditation until they vanish away.
"No thought or intention is ever expelled from the heart except by some other thought or intention incompatible with it....
"Nor must you be afraid that impulses or thoughts of this kind will be imputed to you as sin, so long as your will in no way entangles itself with them..."
(from a letter of St. Anselm, 1095)