"When the intellect begins to advance in love for God, the  demon of  blasphemy starts to tempt it, suggesting thoughts such as no  man but  only the devil [...] could invent. He does this out of envy, so  that the  man of God, in his despair at thinking such thoughts, no  longer dares  to soar up to God in his accustomed prayer. But the demon  does not  further his own ends by this means. On the contrary, he makes  us more  steadfast. For through his attacks and our retaliation we grow  more  experienced and genuine in our love for God."