Whats this principle/theory about duality called?
(a) In metaphysics: Theory which admits in any given domain, two independent and mutually irreducible substances e.g. the Platonic dualism of the sensible and intelligible worlds, the Cartesian dualism of thinking and extended substances, the Leibnizian dualism of the actual and possible worlds, the Kantian dualism of the noumenal and the phenomenal. So, that describes some “types” of dualism, since you were looking for name. Actually, the name of all of those is “metaphysical dualism,” because there is “epistemological dualism” also. But the sentences you used are about metaphysical dualism. (b) In epistemology: Epistemological dualism is the theory that in perception, memory and other types of non-inferential cognition, there is a numerical duality of the content or datum immediately present to the knowing mind and (sense datum, memory image, etc.) and the real object known (the thing perceived or remembered) (cf. A. O. Lovejoy, The Revolt Against Dualism, pp. 15-6). Epistemological
