With the collapse of the old civil society, the Christian basic consensus that had often prevailed in earlier political theory also dissolved. Liberalism, which emerged primarily in Romance countries as "Radicalism," posed the greatest challenge to the old consensus and was significantly promoted by the American and French Revolutions. This volume addresses the key liberal and radical thinkers in Europe and confronts liberalism as a political ideology with competing theories. A concluding chapter is dedicated to the relationship between liberal thinkers and liberal parties in real politics.