Open Science Repository Philosophy

doi: 10.7392/openaccess.70081900

The World Three of Karl Popper

The Open Science Repository


Karl Popper proposed a view of our reality divided into three "worlds", meaning with the word "world" nothing more impressive than a set of things: the world one, the world two and the world three.

This division stands for a better understanding of reality itself, and, as any other theory, it is a way to improve our understanding of some problem; in this case, it improves our understanding of reality and of the universe.

Keywords: world three, Karl Popper, Popper's three worlds.

Citation: Editors. (2013). The World Three of Karl Popper. Open Science Repository Philosophy, Online(open-access), e70081900. doi:10.7392/openaccess.70081900

Published: August 13, 2013

Copyright: © 2013 Open Science Repository. Creative Commons Attribution 3.0 Unported License.


World one

The world one of Karl Popper is the set of physical objects, such as atoms and subatomic particles, natural and artificial materials, bodies, etc. It is the world of matter.

Physical objects are the inhabitants of the world one.

The world one in our planet created -with the emergence of life and animals- the world two.

World two

The world two is the world of subjective experiences; we can call it the world of consciousness. It also includes all other subjective experiences such as feelings, emotions, sensations, etc.

Subjective experiences are the inhabitants of the world two.

The world two on Earth emerged from the development of life. As long as we accept that animals have subjective experiences, the world two began with them. It is mostly characteristic of humans, and in humans it helped the creation of language. Language then created the world three.

The functions of language

Based on Karl Bühler's theory on the functions of language, Karl Popper added an additional function that is fundamental to understand how language creates the world three. Please, note that each superior function includes the inferior ones (the reason why the superior are often confused with the inferior ones).

The first and most inferior of the Bühler's function is simple expression: Even inferior animals and probably plants and microorganism share this function with humans. It is the function that reflects the interior state of the individual, like distress, uneasiness, pain, joy, etc.

The second of the Bühler's function is communication: Communication here means capable of creating an impact on other individuals of the same or other species. Dog barking and other automated behaviors of animals are examples.

The third function of language is description: Description is typical of the human language, although we now know that some bees, probably ants, dolphins and other animals primitively share this function with humans. By being able to describe things, humans advanced communication to another, more precise and potentially diverse level.

Realizing that descriptions could be false or true, Karl Popper added to description the fourth function of critical argumentation: Arguments are, as long as we currently know, exclusive of humans. With arguments (that are themselves descriptions of other things logically and empirically related -compatible, incompatible, etc.- to the assessed description) we can investigate whether a description is true or false, enumerate reasons for such judgement and accept, reject or improve descriptions based on its truthlikeness or falsehood. To sum up, argumentation is a function that improves our set of descriptions, shortening their distance to the truth.

World three

The world three of Karl Popper is the world of products of the two superior functions of language. It is made of abstract objects, ideas, since descriptions of problems, theories and arguments are abstract ideas.

The most important inhabitants of the world three are descriptions of problems, theories intended to solve these problems and critical arguments on the validity of theories.

It is easy to realize that those inhabitants comprise science; thus the world three is the world of science.

The most important feature of the world three, nevertheless, is that its objects, though abstracts, are real. A scientific theory is real and can have strong real effects (effects as important or tragic like the atomic bombings on civilians in 1945 and the life-saving discovery of penicillin), a scientific refutation is also real, and even a false scientific hypothesis (like Newtonian gravitational theory) is a real object that has logical relations with other intellectual abstract objects. Indeed, the current human society is surrounded by world-one objects (such as cars, cities, buildings, technological and industrial goods, services, etc.) that are products of world-three objects (intellectual problems, theories and critical arguments).

Using the content of this site to explain the three worlds, we can say that the PDF files, HTML pages, computer screens, processors, electricity, etc. used to deliver its scientific content are part of the world one of physical objects; the feelings, beliefs and subjective motivations of the authors end editors belong to the world two; however, ideas, problems, theories and arguments contained in each research paper are objects of the world three of abstract intellectual objects.

The world three is autonomous

We can note that the world-three content of each paper is indeed separated from the subjective experiences or knowledge of authors and editors.

The set of abstract objects (descriptions of problems, theories and critical arguments) that exist within the world three are made up by the world two of human minds, but, once produced, gain autonomous existence. These objects, like the content of the research papers in this site, can last longer than their authors and, if preserved, be decoded by intelligent beings in the future, even if the entire humankind disappears.

Euclid's Elements can be understood thousand of years after his death; although its preservation was for hundreds of years dependent on papyrus and books, now the world-one bases of such preservation rely mostly on digital copies and other media. This example shows how the world three of abstract intellectual contents is ontologically autonomous. It depends on the world one for preservation and on the world two for decoding, but its content is another class of abstract things, not physical matter neither subjective experiences.

The world three is an evolutionary invention towards non-violence

Along with photosynthesis, senses, conscience and language, to cite few, the creation of the world three is one of the wonderful inventions of evolution.

Genetic recombination and mutation plus natural selection are ways of problem-solving for the life on Earth. This biological Darwinian process is, however, violent: mutations and recombination are inventions that, if not successful, eventually leads to the death or extinction of the individuals that carry them. Mutations and recombination are "subjective", strictly attached to the body of the individuals.

The creation of the world three of objective, linguistic descriptions of problems, theories and arguments, allows humans to practice problem-solving outside their bodies, firstly in their minds but later with the help of books, published research papers, computer data, etc. New solutions can be imagined, tested and accepted or rejected without the death (negative selection) of their proposers. With the world three, problem-solving on Earth also reached another level, permitting not only a fast and more diverse approach to several different problems but also a process that spare violence and preserve the integrity of our bodies. While a strain of bacteria or a plant species need to rely on successful mutations to explore new ecological niches or defend themselves against harmful conditions, humans can actively search for new niches or fight against bad conditions using intellectual, non-violent problem-solving.

This non-violent aspect of the world three is rarely described when the world three of Popper is explained. Nevertheless, it is of great relevance for humankind.

Science is development of the world three

Doing science is building the ever-evolving world three of objective problems, theories (always conjectural) and arguments.

The Open Science Repository and its authors contribute to the progress of the world three, to the non-violent progress of humankind, by publishing research papers under open access and open review.

Non-human world-three contents

The human-made world-three content is the only known to date. On the dependence of the existence of other intelligent beings in the universe, however, other worlds of intellectual problems, theories and arguments may exist. This is an open possibility.

In the same way we can imagine the existence of other beings in the universe (bodies, world one), even intelligent ones (mind, world two), we can consider the possibility of the existence of other sets of problems, theories and arguments (world-three objects) developed by them.

Thinking about the universe as a great factory of non-violent world-three contents from several sources and of many different ages - million or billion years - is an exciting and motivating image.


Karl R. Popper, Objective Knowledge. Oxford University Press, 1972;

Karl R. Popper, Conjectures and Refutations. Routledge, 1963.

Karl R. Popper, The Logic of Scientific Discovery. Routledge, 1959.

Cite this paper


Editors. (2013). The World Three of Karl Popper. Open Science Repository Philosophy, Online(open-access), e70081900. doi:10.7392/openaccess.70081900


Editors. “The World Three of Karl Popper.” Open Science Repository Philosophy (2013): e70081900.


Editors. “The World Three of Karl Popper.” Open Science Repository Philosophy Online, no. open-access (August 13, 2013): e70081900. doi:10.7392/openaccess.70081900.


Editors, 2013. The World Three of Karl Popper. Open Science Repository Philosophy, Online(open-access), p.e70081900.


1. Editors, The World Three of Karl Popper, Open Science Repository Philosophy Online, e70081900 (2013).


1. Editors. The World Three of Karl Popper. Open Science Repository Philosophy Online, e70081900 (2013).


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