dualism, which is based on the theory that the universe is composed of two essential substances: res cogitans and res extensa. Popperian cosmology rejects this essentialism, but maintains the common sense view that physical and mental states exist, and they interact. The interaction of world2 and world3 The interaction of world2 and world3 is based on the theory that world3 is partially autonomous. For example, the development of scientific theories in world3 leads to unintended consequences, in that problems and contradictions are discovered by world2. Another example is that the process of learning causes world3 to change world2. The interaction of world3 and world1 The world3 objects are embodied in world1. For example, the intrinsic value of Hamlet as a world3 object is embodied many times in world1. But, this representation of an object of world3 in world1 is not considered an interaction in Popper's view. Instead, for Popper, because world3 is a world of abstractions, it can only interact with world1 through world2. See also Eccles' philosophy Platonic realm Third Realm (Frege) Trichotomy (philosophy) Group mind Logical Investigations Notes and abbreviated references References Further reading Concepts in metaphysics Reality Karl Popper