From OpenCog

According to some, a good theory of mind must take into account Objective Reality, Subjective Reality and Intersubjective Reality.

According to others, only Objective Reality "really exists" and the rest are phantoms.

Mind Ontology Links

Subcategory: Objective Reality
Subcategory: Subjective Reality
Subcategory: Polyphonic Reality (or, Intersubjective Reality)
Subcategory: Virtual Reality