Today, we liberal democrats live in a time when nothing less than our liberal democracy is at stake: there is the threat of dictatorship from Russia, and the threat of populism to America and Europe. Populism uses friend-enemy rhetoric to exploit people’s gut feelings to gain power, at the cost of polarising society. In this rhetoric, we can often recognise the political thinking characteristic of Carl Schmitt, in which the enemy is identified as the other or the stranger, whose otherness or strangeness poses an existential threat to ‘our’ way of living. In this thesis, I aim to offer an immanent alternative, which is inspired by Friedrich Nietzsche’s agonal thinking, in which the enemy is perceived not only as a threat, but also as a stimulant to self-overcoming and the transformation of our way of life into a rich plurality of ways of life. I also consider the implications of Schmitt’s thesis of the metaphysical opposition between his own political and Nietzsche’s agonal account of friendship and enmity for different appropriations of their friend-enemy thinking in theories of agonistic democracy. I discuss both Jacques Derrida’s (im)possibility of transcending the friend-enemy dichotomy through a quasi-theological third figure and Chantal Mouffe’s option of transforming friend-enemy antagonism into agonism. But the main question is: How can we liberal democrats use Nietzsche’s and Schmitt’s friend-enemy thinking to better understand and strengthen our liberal democracy?