How do things come to stand for something other than themselves? An understanding of the ontology of relations allows for a compelling account of the action of signs. The Primacy of Semiosis is concerned with the ontology of relations and semiosis, the action of signs. Drawing upon the work of Gilles Deleuze, John Deely, and John Poinsot, Paul Bains focuses on the claim that relations are 'external' to their terms, and seeks to give an ontological account of this purported externality of relations. Bains develops the proposition, first made in 1632 by John Poinsot (John of St. Thomas), that, ontologically, signs are relations whose whole being is in esse ad ('being-toward'). Furthermore, relations are found to be univocal in their being as relations. This univocity of being is antecedent to the division between 'ens rationis' and 'ens reale'. The ontology of relations Bains presents is thus neither mind-dependent nor mind-independent insofar as the rationale of the relation is concerned. The book includes chapters on Deleuze and Deely on relations, Jacob von Uexkull and Heidegger on Umwelten (self-worlds), Maturana and Varela on Autopoieis. It provides the vicarious causality, by way of the scholastic doctrine of the 'species', that is now being resuscitated by Graham Harman and the emerging school of 'object oriented ontology'. The Primacy of Semiosis provides a semiotic that subverts the opposition between realism and idealism; one in which what have been called 'nature' and 'culture' interpenetrate in an expanding collective of human and non-human. Bains' work promises to be a touchstone for semiotic discussion for years to come.