The Heroic Enthusiasts
by Giordano Bruno
This heavily allegorical dialogue by Giordano Bruno is a philosophical discussion of love. At a deeper layer it uses this topic as a mnemonic device to encode a discussion of the nature of the universe, God and the soul. The argument has echoes in Gnostic, Alchemical, Sufi and other esoteric traditions, and some of the poetry is maddeningly similar to Shakespeare (who was a contemporary of Bruno).