“Natural love is "the desire each creature has for its own perfection," and it is by definition without error. Elective love involves free will; it can err by having a wrong object ("per malo obietto") or by being pursued with too much or too little vigor, but it avoids being the cause of sinful pleasure ("mal diletto") when it is directed to the Primal Good (God) or to secondary worldly goods in moderation ("ne' secondi sé stesso misura" [17.98]). Thus, Vergil concludes, love is the cause of every virtue or vice in man (17.103-5).”