Everyone has heard of the term “pseudoscience”, typically used to describe something that looks like science, but is somehow false, misleading, or unproven. Many would be able to agree on a list of things that fall under its umbrella — astrology, phrenology, UFOlogy, creationism, and eugenics might come to mind. But defining what makes these fields “pseudo” is a far more complex issue. Given the virulence of contemporary disputes over the denial of climate change and anti-vaccination movements — both of which display allegations of “pseudoscience” on all sides — there is a clear need to better understand issues of scientific demarcation. Shermer and Gordin explore the philosophical and historical attempts to address this problem of demarcation.