Liberalism has often been considered the most successful political ideology in modern history, coinciding with vast and measurable improvements in human welfare, but recently new threats have arisen in the form of various anti-liberal populist and nationalist movements, which have gained some notable victories in liberal democracies in Europe and America. At the same time, some who self-apply the label ‘liberal’ have at times advocated decidedly illiberal ideas and policies, making the job of those who would defend liberalism from its critics that much more onerous. In the wake of these upheavals, we liberals must cogently recapitulate the core principles of our philosophy and contextualize its role in contemporary society in order to defend it both from the external and internal challenges it faces.