 Poincaré sets out a hierarchical view of the sciences in Science and Hypothesis (1902), although he does not explicitly use this terminology. In his view the special sciences presuppose physics, which presupposes geometry, which in turn presupposes arithmetic. Poincaré treats topics in a serial order—first arithmetic, then geometry, then physics, etc. In the introduction, Poincaré says that “Such is the conclusion we will reach, but to get there, we must first review the sequence of sciences, from arithmetic and geometry to mechanics and experimental physics” (Poincaré 1902, 2017, 2). The hierarchy interpretation has recently come under criticism in an important pair of articles (Dunlop 2016 and 2017). We believe that clarifying what is meant by hierarchy will resolve this debate (see Stump 2017 and Folina 2019 for further discussion). What is the relationship between arithmetic, geometry and the rest of the sciences? Michael Friedman originated the claim that Poincaré presents the sciences in a hierarchy, and in doing so makes clear that what he means by hierarchy is that each lower level must first be in place in order to be able to proceed to the next level: