Why do happily married couples cheat? Why does the modern egalitarian approach to marriage quash desire? Are the heightened expectations we bring to modern love combined with our pursuit of happiness directly related to infidelity? In this special rebroadcast, author and couples therapist Esther Perel tackles the topic of infidelity. Her book "The State of Affairs: Rethinking Infidelity" was released October 10, 2017. Perel is interviewed by Hanna Rosin, co-host of NPR’s Invisibilia.