In an engaging set of essays, Renata Salecl examines “not knowing” from many angles. The Slovenian-British philosopher and sociologist begins by defining he important distinction between ignorance and denial (ignoring known facts). Both can have positive connotations. Human consciousness can easily be overwhelmed by too much information and emotional pain. Both overloads can also lead individuals and societies off the cliff. Among other topics she raises are ethical questions surrounding genetic testing—do you need to know if you have a proclivity for Alzheimer’s or should you pay for sperm from high-achieving donors? Salecl draws attention to the cognitive fatigue of our digital world, where the task of sorting truth from lies has grown more difficult and where—among many Trumpers—dumb ignorance is glorified as “authenticity.”