Structure or system is a ubiquitous and uneliminable feature of all our experience and theory, and requires an ontological analysis. The essays collected in this volume provide an account of structure founded upon the proper analysis of polyadic relations as the irreducible and defining elements of structure. It is argued that polyadic relations are ontic predicates in the insightful sense of intension-determined agent-combinators, monadic properties being the limiting and historically misleading case. This assay of ontic predicates has a number of powerful explanatory implications,...