Popper's three worlds

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Popper's three worlds is a way of looking at reality, described by the Austrian philosopher Karl Popper in a lecture in 1978.[1] The concept involves three interacting worlds, called World 1, World 2 and World 3.[2]

Worlds 1, 2 and 3

Popper split the world into three categories:

  • World 1: the world of physical objects and events, including biological entities
  • World 2: the world of mental objects and events
  • World 3: objective knowledge.

The interaction of World 1 and World 2

The theory of interaction between World 1 and World 2 is an alternative theory to Cartesian 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.

World 3

Popper's world 3 contains the products of thought. This includes abstract objects such as scientific theories, stories, myths, tools, social institutions, and works of art.[2]

The interaction of World 2 and World 3

The interaction of World 2 and World 3 is based on the theory that World 3 is partially autonomous. For example, the development of scientific theories in World 3 leads to unintended consequences, in that problems and contradictions are discovered by World 2. Another example is that the process of learning causes World 3 to change World 2.

The interaction of World 1 and World 3

Contained in World 3 are also things as feats of engineering and art. The World 3 objects, although extant in World 1, are embodied and given extra meaning by World 3. For example, the intrinsic value of Hamlet as a World 3 object has many embodiments in World 1, the physical world. This idea would be something along the lines of a meta-object, or a form of a being.


  • Objective Knowledge: An Evolutionary Approach, 1972
  • The Self and Its Brain: An Argument for Interactionism (with Sir John C. Eccles), 1977
  • The Open Universe: An Argument for Indeterminism, 1982
  • Knowledge and the Body-Mind Problem, 1994.

See also


  1. Three Worlds by Karl Popper - The Tanner Lecture on Human Values - Delivered by Karl Popper at The University of Michigan on April 7, 1978.
  2. 2.0 2.1 Heller, Michael. Philosophy in Science: An Historical Introduction. Springer, 2011, p. 118ff.

External links