Who would have imagined that we'd be disputing the fact of “facts”? Yet, the Trump administration routinely accuses the media and its opponents of “lying” and a counsellor to the president, Kellyanne Conway, has added the phrase “alternative facts” to our political vocabulary.  President Donald Trump is giving expression to a process that has been building for some time. Opinions mask as evidence on social media that do not always engage in fact checking.  A public that is not very good at separating fact from fiction, at spotting weak arguments, and sniffing out skimpy evidence is a real challenge in a democracy. So, how did we get from truth to "truthiness"? In his new book, A Field Guide to Lies: Critical Thinking in the Information Age, author Daniel Levity walks us through common mistakes we all make that leave us vulnerable to weak arguments and faulty evidence.  Levitin is the James McGill Professor of Psychology and Neuroscience at McGill University and a faculty member at the Haas School of Business at the University of California, Berkeley.