The man that hath no music in himself
Lorenzo:
"The man that hath no music in himself,
Nor is not mov'd with concord of sweet sounds,
Is fit for treasons, stratagems, and spoils."
Jessica, daughter of Shylock, has eloped with Lorenzo, and they are sitting in the moonlight delighting in each other's company. When musicians enter, Jessica remarks that she is never happy when she hears sweet music and that instead it makes her sad. Lorenzo explains to her that the sadness she feels is the hearkening of her soul to celestial powers. It was a basic assumption among Elizabethans that the musical harmony of the spheres (planets, moon, sun) was a manifestation of the universal Order in which God created heaven and earth. Lorenzo reminds Jessica that music affects even wild beasts, and that nothing in nature is immune to its ability to determine human emotion. "Mark the music."