Further examples of ontological questions include:[citation needed] What is existence, i.e. what does it mean for a being to be? Is existence a property? Is existence a genus or general class that is simply divided up by specific differences? Which entities, if any, are fundamental? Are all entities objects? How do the properties of an object relate to the object itself? What features are the essential, as opposed to merely accidental attributes of a given object? How many levels of existence or ontological levels are there? And what constitutes a 'level'? What is a physical object? Can one give an account of what it means to say that a physical object exists? Can one give an account of what it means to say that a non-physical entity exists? What constitutes the identity of an object? When does an object go out of existence, as opposed to merely changing? Do beings exist other than in the modes of objectivity and subjectivity, i.e. is the subject/object split of modern philosophy inevitable? [edit]Concepts Essential ontological dichotomies include: Universals and particulars Substance and accident Abstract and concrete objects Essence and existence Determinism and indeterminism