Extended simples are physical objects that, while spatially extended, possess no actual proper parts. The theory that physical reality bottoms out at extended simples is one of the principal competing views concerning the fundamental composition of matter, the others being atomism and the theory of gunk. Among advocates of extended simples, Markosian’s ‘MaxCon’ version of the theory (Aust J Philos 76:213–226, 1998, Monist 87:405–428, 2004) has justly achieved particular prominence. On the assumption of causal realism (i.e., on the assumption that a Humean account of causation is false), I argue here that the reality of MaxCon simples would entail the reality of irreducible, intrinsic dispositional properties. The existence of dispositional properties in turn has important implications for another central debate in metaphysics, namely that between two major competing views concerning the ontology of laws: dispositionalism versus nomological necessitarianism.