English: An illustration of the ontologies of dualism versus monism showing how physical substance relates to mental substance (i.e. body & mind) as either fundamental or derivative. Monism is further divided into physicalism, idealism, or neutral monism where the physical and mental are both derivative of a third substance that is neither body nor mind.

An alternative term for derivative is emergent. For example, a typical ontology held by physicists is that the physical realm is fundamental, and the phenomenon of consciousness is emergent from that (physicalism). Likewise, a typical ontology held by many in religion is that spirit is fundamental, with both mind and matter being emergent from that (neutral monism).