  In the current philosophical landscape, there are many different forms of pluralism on offer. For instance, there is an ontological form of pluralism (there are different ways of being), truth pluralism (there are different ways of being true), and there is a logical form of pluralism (there is more than one correct logic; see the entry on logical pluralism). However, it is almost universally assumed, if mostly unstated, that there can be no pluralism about the actual world—this one is the only actual one. As should appear clear from this entry, though, Sylvan was accustomed to challenging the philosophical consensus. He began by attacking classical logic, he continued by questioning the so-called Ontological Assumption and, late in his career, he decided to challenge what he calls one-world-ism, that is, the idea that there is only one actual world.