 Generally understood, an individual replicates itself and possesses anatomic borders, a harmonious communication between its parts, a division of labor for the benefit of the whole, and a system of hierarchical dominance and control. By these criteria, the immune system is responsible for establishing and maintaining the integrity of such an individual (Pradeu 2016). However, symbiosis challenges this entrenched definition of the individual organism: shared physiologies govern homeostasis; anatomic margins lose clear definition; development is intertwined among several phylogenetically defined entities; and the unit of evolutionary selection becomes a multiplex genome (see the entry on  the biological notion of individual).  On this consortium view, notions of individuality are replaced with complexes of organisms that defy any singular definition of organismal identity as independent agents (Löwy 1991; S. Gilbert, Sapp, and Tauber 2012). In terms of commensal relationships, symbiosis, mediated by immune tolerance, signifies stabilized adaptation to the complex of diverse living elements that live in a cohesive ecology, both within and external to the traditional borders of the organism. When oriented by ecological relationships, immunology moves from its dominant concern with autonomous individuality to include the science of cooperative assemblies of organisms. The ontological implications of this re-formulation are highly significant for philosophical considerations of identity as discussed below (see the entry on  identity).