Chapter 17 on Friendship

Love holds the first rank among the passions of the soul. Be careful therefore, my dear Philothea, to avoid entertaining any evil love whatsoever. For if you do, you will all too quickly become evil yourself. If what they exchange are false and empty goods, then the friendship is also false and empty. However, if they be true, the friendship is likewise true. And the more excellent the goods, the more excellent also is the friendship.