From early in his career (and for many years after), Sylvan defended a sophisticated Meinong-inspired ontology (which he called "noneism"), first presented in his 1966 paper, "Some Things Do Not Exist." After several more papers in the 1970s, the theory was given a book-length treatment in 1980, "Exploring Meinong's Jungle and Beyond". The view—also defended in recent years by Priest—utilizes a modal theory including "impossible worlds" to deal with supposed objects, like the "round square." Sylvan's formulation is logically consistent, and avoids certain paradoxes associated with Meinong's original ontology; although, like many Meinongian views, it faces criticism due to its presumed ontological implausibility.