What is Ontology?
Ontology is a branch of metaphysics that deals with reality itself, as apart from the subjective impressions and thoughts of the person who experiences it. The term was introduced by Christian von Wolff to designate a field of speculative thought lying between natural philosophy, which deals with the origins and the structure of the world, and mental philosophy, or psychology, dealing with the mind.
Ontology, he taught, should find the answers to questions more basic than those considered in either natural philosophy or psychology.
There is a reality that gives rise to sensations. Obviously, the sensations are quite different from the "thing-in-itself" that stimulates them. Light waves, for example, are not the same as the colors that are , experienced by the human observer.
They are the "thing-in-itself" or an aspect of reality that gives rise to particular types of sensations.
Ontology is the speculative inquiry that asks whether reality is basically one entity with a diversity of manifestations or a multiplicity of entities.
In either case, the major categories and relationships must be discovered if reality is to be thought of as a coherent, unified entity subject to the laws of formal logic. If there is a multiplicity of entities in reality, then ontology must defend the pluralistic doctrine. Concepts developed in modern theoretical physics have furnished many new problems for philosophers who believe that ontology is one of the most challenging areas for speculative thought about reality as reality.