Conferences of St. John Cassian - Conference Seven on the Changeableness of the Soul and on Evil Spirits Part III

The elder Serenus clarifies for Cassian and Germanus that the evil spirits, although capable of working in a kind of temporary accord, do not act in harmony with each other.  Rather, a spirit must set out by itself to attack the mind in such a way that if it departs vanquished it gives it over to another spirit to be attacked more vehemently.  Not all evil spirits are as powerful or fight with the same ferocity and with beginners and the weak only the weaker spirits are paired off in battle.  The picture Serenus paints is of constant and intense warfare that only grows in its intensity with growth in virtue and holiness.  The individual must learn to fight relentlessly and seek to completely defeat the enemy; developing a hatred for sin.  If the power of demons seem blunted in our day in comparison to the early days of the anchorites it is most likely due to our negligence having made them milder and made them disdain to fight as they did against the more accomplished soldiers of Christ.  This kind of a battle is used often by God to purify the soul of even the slightest sins; he chastises the ones whom he loves and scourges every son he receives in order to perfect them.