Monism

Monism is the claim that there is one reality, not two separate realms that must somehow be bridged — not phenomena and noumena, and not mind and matter. Cartesian dualism created the interaction problem (how do mind and body interact if they are fundamentally different substances?); Kantian dualism created the knowledge problem (how can we claim knowledge of reality if we only ever access appearances structured by our own categories?).

Critical realism is monist in that observable events, unobservable mechanisms, experienced phenomena, and underlying structures are all part of one ontological realm operating by the same fundamental principles — while still being stratified into levels. This monism does not flatten everything to a single level, as empiricism does when it reduces reality to the observable.

Discussed in chapter-03 §II.i.