This article aims to show that fundamentality is construed differently in the two most prominent strategies of analysis we find in physical science and engineering today: (1) atomistic, reductive analysis and (2) Systems analysis. Correspondingly, atomism is the conception according to which the simplest (smallest) indivisible entity of a certain kind is most fundamental; while systemism, as will be articulated here, is the conception according to which the bonds that structure wholes are most fundamental, and scale and/or constituting entities are of no significance whatsoever for fundamentality. Accordingly, atomists maintain that the basic entities—the atoms—are fundamental, and together with the “external” interactions among them, are sufficient for illuminating all the features and behaviors of the wholes they constitute; whereas systemists proclaim that it is instead structural qualities of systems, that flow from internal relations among their constituents and translate directly into behaviors, that...