What is the lesson in sonnet 307 by Petrarch?

The lesson in Sonnet 307 by Petrarch is that true beauty lies not in physical appearance but in the virtue and kindness of a person. Petrarch praises his beloved for her inner qualities and highlights how her compassionate and gentle nature makes her truly beautiful. The poem suggests that physical beauty is fleeting and unreliable while inner virtues last a lifetime and make one truly worthy of love and admiration.