Abstract

The paper presents three main definitions of theoretical entity: basic definition, definition from unobservability, and ontological definition. These are the definitions of theoretical entity that are most popular and widely accepted by philosophers of science (both realists and antirealists). All these definitions contain significant defects, which lead to unacceptable conclusions. The author also offers an alternative definition from explanation, which avoids the defects of previous definitions. The aim of the paper is to prove that proper definition of theoretical entity is necessary in debates over scientific realism. To make a legitimate claim about the existence of theoretical entities, one should know what theoretical entity really is.