Can an Alzheimer’s patient with dementia so severe she can’t remember her daughters’ names or how to eat a hamburger consent to have sex with her husband? That’s the stark question raised by the case of Henry Rayhons, the former Iowa state legislator who, as the New York Times reported last week, has been charged with third-degree felony sexual assault for allegedly raping his wife, Donna Lou Rayhons, in her nursing home. To John Portmann, a religious studies professor at the University of Virginia and the author of The Ethics of Sex and Alzheimer’s...