Previous research that connected Lessing and Nietzsche confined their engagement, on the one hand, largely to individual aspects of kindredship in thought and writing. On the other hand, Nietzsche's judgments of Lessing have mostly been arranged in rather short compilations of text passages while neglecting many connecting and contextual aspects of interpretations. This investigation aims for two goals. 1. All published text passages in which Nietzsche explicitly deals with Lessing are interpreted in a detailed, connecting, and contextual manner. The Nachlass is only used cautiously and selectively. 2. An attempt is made to connect the kindred elements of Lessing and Nietzsche in a common root of thought: in their tendencies towards philosophical Fluktuanz. Starting from the explicit text passages, a common semiotic and epistemological frame of Lessing's and Nietzsche's thought and writing is drafted, from which the interpretation goes back to the text again. The investigation produces the following results: 1. Nietzsche's judgments of Lessing as an honest critic, a searching classic, a brave dialectician, as the trigger of nihilism in art and as an Anpflanzer of a cosmopolitan European culture refer back to Nietzsche's own perceptions of freier Geist, of agonal thinking, and of the dynamic Fluktuanz of the wills to power. 2. Especially in Lessing's late work, many elements can be shown that indicate his tendency towards philosophical Fluktuanz. Insofar Lessing and Nietzsche questioned distinctions and notions of their times from a perspectivistic approach and in insofar they established new distinctions on their own responsiblility, they could both be regarded as following the ideal of freier Geister. Lessing's and Nietzsche's actuality can be highlighted by their tendency towards philosophies of Fluktuanz. These philosophies can be characterized by their openness and dynamic flexibility, which are essential for orientation within different incommensurable cultures and perspectives in a globalized world.