From President Donald Trump to the rise of new nationalist political parties in Europe to a general resurgence of the term in recent years, nationalism seems to be on the march. Nationalism is a political movement that has made major inroads in recent years while preaching a message of immigration restrictionism, trade protectionism, and a stronger government devoted to defending citizens from (mostly) imaginary harms. But besides some policy positions and a style of governance, there is not a good working definition of nationalism widely used in popular discourse and there is almost no attempt to distinguish it from patriotism. My base assumption was that nationalism must be something more than crude jingoistic tribalism, but few ventured beyond that. Those reasons prompted me to read several thousand pages on the topic – and I learned quite a bit. Below are some lessons I learned and a useful taxonomy of different types of nationalism.