Neither Creator nor creature can be without love, but if this love is turned aside to evil, then the creature goes against the creator . . . A man may love evil by willing evil to his neighbors in three ways: For first, he may hope to be prosperous through his neighbor’s degradation; and again, he may himself fear to lose power, grace, honour, or reputation because of his neighbour’s advancement, and may therefore be miserable at that advancement; and again, he may feel himself injured by his neighbour, and wish to be revenged, so that he sets himself to seek out the other’s hurt.
Dante: Purgatory.