Historians working in the Humboldtian tradition developed ideas that would become central in Boasian anthropology. Leopold von Ranke defined the task of the historian as "merely to show as it actually was", which is a cornerstone of Boas's empiricism. Wilhelm Dilthey emphasized the centrality of "understanding" to human knowledge, and that the lived experience of an historian could provide a basis for an empathic understanding of the situation of an historical actor.[43] For Boas, both values were well-expressed in a quote from Goethe: "A single action or event is interesting, not because it is explainable, but because it is true.