Conventional wisdom dictates that those goods which are said to cause harm or impose costs on society deserve a special tax. For centuries, governments have levied these "sin taxes" on alcohol and tobacco, but the list of taxable sins has now grown to include soda and marijuana, with calls to impose further taxes on plastic bags, meat, and even robots and carbon. Contrary to what experts and policymakers tell us, many of these alleged sins impose very little, if any, cost on society, and the harms that do exist can be minimized without resorting to tax. What follows in this book is a discussion of four case studies—on tobacco, marijuana, alcohol and soda—which make the case against the conventional wisdom in taxing these "sins", before concluding that when it comes to taxing sin, it is time for governments to forgive—and forget.