The volume collects essays by an international team of philosophers aimed at elucidating three fundamental and interconnected themes in ontology. In the first instance, there is the issue of the kind of thing that, in the primary sense, is or exists: must the primitive terms be particular or universal? Any reply will itself raise the question of how to treat discourse that appears to refer to things that cannot be met with in time and space: what difference is there between saying that someone is not sad and saying that something does not exist? If we can speak meaningfully about fictions, what makes those statements true (or false) and how can the entities in question be identified? Assessment of the options that have been opened up in these fields since the work of Bertrand Russell and Alexius Meinong at the beginning of the twentieth century remains an important testing-ground for metaphysical principles and intuitions.