In this chapter, different ways of interpreting the mathematics of the past are problematized, drawing on examples that range from archeological artifacts to written sources from the ancient Egyptian, Babylonian, and Greek civilizations. The distinction between history and heritage is explored through the cases of Euler’s function concept, Cauchy’s sum theorem, and Euclids’ Elements. The contrast between the historical past and the practical past, as well as between historical and nonhistorical relations to the past, is further illustrated through Torricelli’s seventeenth-century result on an infinitely long solid. Two complementary perspectives for analyzing mathematics across time—the synchronic and diachronic approaches—are introduced, with particular relevance to the history of school mathematics. Debates and polemics between different historiographical schools are intentionally set aside, since such “histrionics” shift attention away from the mathematical ideas themselves and toward issues that do not advance our understanding of them. In addition, the chapter questions the theory of recapitulation—the claim that students’ conceptual development mirrors the historical development of mathematics—by emphasizing the decisive role of culture in shaping mathematical thought.