[Virgil speaking to Dante]:

“‘My son, there’s no Creator and no creature
Who ever was without love—natural
Or mental; and you know that,’ he began.
‘The natural is always without error,
But mental love may choose an evil object
Or err through too much or too little vigor.
As long as it’s directed toward the First Good
And tends toward secondary goods with measure,
It cannot be the cause of evil pleasure;
But when it twists toward evil, or attends
To good with more or less care than it should,
Those whom He made have worked against their Maker.
From this you see that—of necessity—
Love is the seed in you of every virtue
And of all acts deserving punishment.'”

—from Canto XVII Dante’s Purgatorio by Dante Alighieri