The aim of this article is to develop Kenneth N. Waltz’s conceptualization of system structures based on the distribution of capabilities to those described by two traits at system-level: the distribution of capabilities across states and states’ geographic positions with respect to each other, that is, the contiguity configuration. The development generates taxonomies of structures evaluated as mental pictures that guide, organize, and channel thoughts by identifying the ways system structures constrain international interactions. Mental pictures are argued to derive from a multiplicity of interrelated neurophysiological processes of the brain according to functionalism which is a monist doctrine of the philosophy of mind. Mental pictures establish structural constraints as products of an algorithm based on realism and system theory depicting a neo-Kantian view of how our minds impose order on sensory data.