# Popper's three worlds

Popper's three worlds is a way of looking at and understanding reality, developed by the British philosopher Karl Popper in many lectures and books, for example "Objective Knowledge - An Evolutionary Approach" (1972) and "The Self And Its Brain" (1977). Popper's theory involves three interacting worlds, called world 1, world 2 and world 3.

## Worlds 1, 2 and 3

These three "worlds" are not proposed as isolated universes but rather are realms or levels within the known universe.
Their numbering reflects their temporal order within the known universe and that the later realms emerged as products of developments within the preceding realms. A one-word description of each realm is that World 1 is the material realm, World 2 is the mental realm, and World 3 is the cultural realm - though, in the detail of Popper's theory, each "World" or realm transcends what might be typically understood by the respective terms "material", "mental" and "cultural".
Popper's theory of these three "worlds" is evolutionary and cosmological. As is consistent with the known universe as presently described by the natural sciences, Popper maintains that the known universe did not contain any World 2 or World 3 at its inception - at its inception there was only a "World 1", a realm where everything consisted of physical states and processes. Moreover, that "World 1" was for a very long time devoid of any living matter, and was for that time a World 1 lacking any biological level. The biological level is a level within World 1 that emerged from its physical-chemical evolution over a vast tract of time, as a lifeless universe eventually gave rise to living organisms, such as those on earth. In a similar sense to this emergence of life within World 1 itself, Popper maintains that a "World 2" of mental life later emerged as a product of biological evolution, and that subsequently a "World 3" of cultural objects emerged as a product of evolution within the human "World 2". This cosmological approach is directly opposed to any form of reductionism that argues that we can ultimately explain whatever comes later in the known universe in terms of what came before. Against this, Popper argues that we should instead see the universe as "creative" and indeterministic, and as having given rise to genuinely new levels or realms - like biological life, "World 2" and "World 3" - that were not there from its beginning and which are not fully 'reducible' to (or fully explicable in terms of) what was there at its beginning.
The three worlds may be understood, in terms of this evolutionary and cosmological framework, as containing three categories of entity:
* World 1: the realm of states and processes as studied by the natural sciences.
These include the states and processes that we seek to explain by physics and by chemistry, and also those states and processes that subsequently emerge with life and which we seek to explain by biology.
* World 2: the realm of mental states and processes.
These include sensations and thoughts, and include both conscious and unconscious mental states and processes. World 2 includes all animal as well as human mental experience. These mental states and processes only emerge as a product of biological activity by living organisms, and so only emerged subsequent to the emergence of living organisms within World 1. Mental states and processes are the products of evolutionary developments in the World 1 of animal brains and nervous systems, but constitute a new realm of World 2 that co-evolved by its interaction with the World 1 of brains and nervous systems.
* World 3: the realm of the 'products of thought' when considered as objects in their own right.
These products emerge from human "World 2" activity, but when considered as World 3 objects in their own right they have rebound effects on human World 2 thought processes. Through these rebound effects, World 3 'objects' may - via World 2-based human action on World 1 - have an indirect but powerful effect on World 1. In Popper's view, World 3 'objects' encompass a very wide range of entities, from scientific theories to works of art, from laws to institutions.
Popper makes two key claims regarding the role of World 3 in the known universe. First, Popper argues that, despite the many continuities and correspondences between the human and animal World 2, (1) only humans consider their mental products as objects in their own right in a World 3 sense and (2) only humans have access to World 3 objects. Second, World 3 has no direct effect on World 1 but only affects World 1 as mediated by the human World 2: for example, a theory of nuclear reactions will never of itself cause a nuclear reactor to be built, yet the existence of a nuclear reactor is not the result of a purely World 1 process but is the eventual product of complex interactions between particular World 3 theories and human World 2 mental activity, and also particular World 2 and World 1 mind-brain-body interactions, leading to particular World 1 human actions (to construct a nuclear reactor) only made feasible by this complex set of interactions.

## More on world 3

Popper's world 3 contains the products of thought. This includes abstract objects such as scientific theories, stories, myths and works of art. Popper says that his world 3 has much in common with Plato's theory of Forms or Ideas. But, world 3 is not to be conceived as a Platonic realm, because unlike the Platonic world of forms, which is non changing and exists independently of human beings, Popper's world 3 is created by human beings and is not fixed. It corresponds to the current state of our knowledge and culture.

## 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.

## 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 3 and world 1

The world 3 objects are embodied in world 1. For example, the intrinsic value of Hamlet as a world 3 object is embodied many times in world 1. But, this representation of an object of world 3 in world 1 is not considered an interaction in Popper's view. Instead, for Popper, because world 3 is a world of abstractions, it can only interact with world 1 through world 2.