More on Karl Popper’s Three World Ontology

Karl Popper’s Three Worlds system is a pluralist ontology that classifies all objects in our universe, even though it is quite different from dualism. Ultimately, all objects in Popper’s world are causally dependent on matter and energy and their relations and permutations, so that, despite being pluralist, it has a fundamental physicalist/materialist nature.

These worlds, as noted in an earlier post, can be described as follows (but should be read from the bottom at “World 1” upwards):

World 3: both (a) unembodied objects such as abstract entities (and, most probably, universals), mathematical entities, social institutions and objective knowledge, and (2) embodied entities* that are products of human design, engineering and production such as buildings, books, clothes, money, and art works;
↑World 2: the world of conscious minds with intentionality and mental states;
↑World 1: the spatiotemporal world of physical objects and events, matter and energy and even biological system considered merely as complex physical systems.

As noted before, Popper’s three world ontology – or threefold realism – avoids the fallacy of strong reductionism, makes sense of abstract objects and downwards causation, and is compatible with a methodological pluralism in the social sciences.

It is also used by Jesper Jespersen (2009) in his methodology for Post Keynesian economics, and seems compatible with the Critical Realism used by other Post Keynesians such as Tony Lawson, Philip Arestis, Victoria Chick, and Sheila Dow.

Popper’s World 2 consists of conscious minds and the mental or psychological world, with all feelings, thoughts, beliefs, perceptions and sense experiences. It can be further divided into (1) fully conscious experiences, (2) dreams or hallucinations, (3) subconscious experiences, (4) human minds and (5) animal minds (Popper 1978: 143). In contrast to eliminative materialism, Popper defends the real existence of mental states in World 2.

World 3 contains all the abstract cultural products of the human mind, from languages, texts of books, fictions, religious myths, scientific conjectures and theories, mathematical entities and theories, songs and music, art work, and feats of engineering, construction and design.

Many, though not all, World 3 objects are embodied or physically realized (or instantiated) in the physical objects of World 1. A painting by a great artist, for example, exists in one form, but in contrast books or plays can be embodied in many different physical forms. World 3 “objects themselves are abstract objects, and that their physical embodiments or realizations are concrete objects” (Popper 1978: 145).

One important point is that Popper’s argument for realism uses causality and downwards causation as arguments in favour of his view:

“what is real or what exists is whatever may, directly or indirectly, have a causal effect upon physical things, and especially upon those primitive physical things that can be easily handled.

Thus we may replace our central problem of whether abstract world 3 objects such as Newton’s or Einstein’s theories of gravitation have a real existence, by the following problem: can scientific conjectures or theories exert, in a direct or indirect way, a causal effect upon the physical things of world 1? My reply to this question will be: yes, they can indeed. ....

My fundamental argument in support of world 3 realism is very simple. We all know that we live in a physical world 1 which has been greatly changed by making use of science; that is to say, by using world 3 conjectures or theories as instruments of change. Therefore, scientific conjectures or theories can exert a causal or an instrumental effect upon physical things; far more so than, say, screwdrivers or scissors.” (Popper 1978: 153–154).

Popper’s view of mathematics is also interesting:

“Children learn to count. This is a skill, a man-made invention. We learn so to count that we can construct to any given number its successor number, without end. So we come to understand the infinite sequence of natural numbers. But since it is infinite, there is no physical realization, no embodiment of this sequence. Nevertheless the sequence of natural numbers is a world 3 object about which we can make many discoveries. Thus we discover that all numbers (and ‘all numbers’ means infinitely many) are either odd or even. And we discover that certain numbers, such as 2, 3, 5, 7, 11, 13, are prime numbers, that is to say, not divisible. (Of course, all numbers are either divisible or prime.) And we even discover Euclid’s theorem, according to which, although prime numbers become rarer and rarer when we proceed in the sequence of natural numbers, they never peter out completely: Euclid’s theorem says that there are infinitely many prime numbers within the infinite sequence of natural numbers.

It is of course perfectly true that all these discoveries are the results or products of thought processes: what I call world 3 is, indeed, the world of the products of the human mind; that is, the products of world 2. But the infinite sequence of natural numbers is, clearly, an abstract world 3 object; and it is an object that we can investigate, and about which we can make quite unexpected discoveries. In fact, there are many open problems about this object, problems of number theory which mathematicians have failed to solve so far.
....

I have stressed that the sequence of the natural numbers, since it is infinite, cannot be physically realized, or embodied. It is an unembodied, an abstract world 3 object. The same holds for every conjecture or theory, if we identify a conjecture or theory – that is, its logical content – with the system of all the theorems that can be derived in it; that is to say, with the corresponding deductive system. Such a theory, or such a system, is infinite, and may be full of surprises. Thus it must have been a surprise for Einstein when he found, shortly after writing his first paper on Special Relativity, that the now-famous formula E = mc2 could be deduced from it as a theorem.” (Popper 1978: 161–162).

Finally, Popper sums up his ontology as follows:

“To sum up, we arrive at the following picture of the universe.

There is the physical universe, world 1, with its most important sub-universe, that of the living organisms.

World 2, the world of conscious experience, emerges as an evolutionary product from the world of organisms.

World 3, the world of the products of the human mind, emerges as an evolutionary product from world 2.

In each of these cases, the emerging product has a tremendous feedback effect upon the world from which it emerged. For example, the physico-chemical composition of our atmosphere which contains so much oxygen is a product of life – a feedback effect of the life of plants. And, especially, the emergence of world 3 has a tremendous feedback effect upon world 2 and, through its intervention, upon world 1.

The feedback effect between world 3 and world 2 is of particular importance. Our minds are the creators of world 3; but world 3 in its turn not only informs our minds, but largely creates them. The very idea of a self depends on world 3 theories, especially upon a theory of time which underlies the identity of the self, the self of yesterday, of today, and of tomorrow. The learning of a language, which is a world 3 object, is itself partly a creative act and partly a feedback effect; and the full consciousness of self is anchored in our human language.

Our relationship to our work is a feedback relationship: our work grows through us, and we grow through our work.

This growth, this self-transcendence, has a rational side and a non-rational side. The creation of new ideas, of new theories, is partly non-rational. It is a matter of what is called ‘intuition’ or ‘imagination’. But intuition is fallible, as is everything human. Intuition must be controlled through rational criticism, which is the most important product of human language. This control through criticism is the rational aspect of the growth of knowledge and of our personal growth. It is one of the three most important things that make us human. The other two are compassion, and the consciousness of our fallibility.” (Popper 1978: 166–167).

BIBLIOGRAPHY
Jespersen, Jesper. 2009. Macroeconomic Methodology: A Post-Keynesian Perspective. Edward Elgar, Cheltenham, Glos. and Northampton, MA.

Popper, Karl R. 1978. “Three Worlds,” The Tanner Lecture on Human Values, Delivered at the University of Michigan, April 7, 1978.
www.thee-online.com/Documents/Popper-3Worlds.pdf‎