Ontology (philosophy)

In philosophy the field of 'ontology considers what things exist, and what existence implies.

For some philosophers, called 'deflationist', this question is linguistic, that is, it concerns the usage of expressions like 'At least one such-and-such exists'. Such expressions are called existential expressions.

For other philosophers, ontology concerns the actual existence of real things in the universe. The subject is complicated by discussion of issues like whether compound objects really exist, a question of mereology. For example, does a 'book' exist or only the 'pages' of the book. How do we draw the line between 'sensible' compound objects and silly ones like 'my nose and the Eiffel tower'?