From W. Ross Ashby comes the famous Law of Requisite Variety which states that the variety of actions available to a control system must be at least as large as the variety of actions in the system to be controlled. Now, constructivism certainly comes in a huge variety of forms and versions. I felt challenged to get some grip on its sumptuousness — especially because people regularly ask me to provide some sort of overview. In fact they sometimes express their astonishment that what they considered a monolithic epistemology turns out to be a dappled one. I have to admit that also for me it took some time to recognize the jungle as such and some more time to find my way through it. Please find below a (certainly still crude) version of the requested guide. Suggestions and corrections are welcome.

Refer to this pages as: Riegler, A. (2003) The Key to Radical Constructivism.

Last update: 28 Nov 2003. Copyright by Alexander Riegler ©2003.
Part of the Radical Constructivism Homepage
Send suggestions and corrections to ariegler[at]



Horizontal dimension

  • Philosophical / Epistemological
  • Cybernetic
  • Psychological / Cognitive
  • Biological / Neurobiological
  • Physical
  • Psychiatrist / Therapeutic
  • Literature / Media Sciences
  • Computational
  • Social
  • System Theoretical
  • Pedagogical

Vertical dimension

  • Trivial (or modest constructivism)
  • Radical (or meta-constructivism)

Four Postulates of RC

  1. Radical Constructivist Postulate
  2. Epistemological Corollary
  3. Methodological Corollary
  4. Limitation of Construction Postulate


  • Biology of Cognition
  • Second Order Cybernetics
  • Constructivist Evolutionary Epistemology
  • Theory of Sensorimotor Contingencies

Further constructivisms

  • Constructive Realism
  • Mathematical constructivism
  • Erlangen Constructivism
  • Constructionism
  • Russian Constructivism


This text is a patchwork collected from my following publications:

  1. Turing’s choice: Human and artificial volition. In: Fischer, R. & Macallister, C. (eds.) Artificial Intelligence: Exploring Critical Issues, forthcoming.
  2. Konstruierte oder konstruierende Seele? Gedanken zum Seelebegriff aus kognitiv-konstruktivistischer Perspektive. In: Peschl, M. (ed) Auf der Suche nach dem Konzept/Substrat der Seele. Würzburg: Königshausen und Neumann, forthcoming.
  3. Whose Anticipations? In: Butz, M., Sigaud, O., and Gerard, P. (eds.) Anticipatory Behavior in Adaptive Learning Systems: Foundations, Theories, and Systems. Lecture Notes in Artificial Intelligence. Springer-Verlag, pp. 11-22, 2003.
  4. A Better World. Karl Jaspers Forum: An Electronic Journal for Target Articles TA40 C4, 2002.
  5. Towards a Radical Constructivist Understanding of Science. Foundations of Science, special issue on “The Impact of Radical Constructivism on Science” 6(1-3): 1-30, 2001.
  6. Virtual Science. Virtuality and Knowledge Acquisition in Science and Cognition. (with M. Peschl) In: Riegler, A. et al. (eds.) Virtual Reality. Peter Lang Verlag: Frankfurt/M., pp. 9-32, 2001.
  7. Moving On With Constructivism (Invited comment). Karl Jaspers Forum: An Electronic Journal for Target Articles TA25 C15, 2000.
  8. Does Representation Need Reality? (with M. Peschl) In: Riegler, A., Peschl, M. & Stein, A. v. (eds.) Understanding Representation in the Cognitive Sciences. New York: Plenum Press, pp. 9-17, 1999.
  9. Ein kybernetisch-konstruktivistisches Modell der Kognition. In: Müller, A, Müller, K. H. & Stadler, F. (eds.) Konstruktivismus und Kognitionswissenschaft. Kulturelle Wurzeln und Ergebnisse. Wien, New York: Springer, pp. 75-88, 1997.

and from the following invited talks:

  1. “Under Construction” at the International Heinz von Foerster Congress “Knowledge - Organization - Society,” Wittgenstein-Haus, Vienna, 13 November 2003.
  2. “Construction of Arbitrariness and Arbitrariness of Construction” at the Heinz von Foerster Symposium, Vienna, Austria, 13 November 2002.
  3. “Wer konstruiert wirklich? Gedanken zum Seelebegriff aus kognitiv-konstruktivistischer Perspektive” [Who constructs really? The notion of “soul” from a cognitive-constructivist perspective] at the fourth “Die Seele” symposium on “Die Rolle der Seele aus der Perspektive der Cognitive Science und des Artificial Life,” Vienna, Austria, 10 November 2001.
  4. “Het constructivistische wereldbeeld: Implementatie en consequenties” [The Constructivist World View: Implementation and Consequences] at the Centrum voor Logica en Wetenschapsfilosofie, Brussels, Belgium, 8 November 2001.
  5. “Science from a Radical Constructivist Point of View” at the University of Freiburg, Germany, 22 August 2000.
  6. “Ein kybernetisch-konstruktivistisches Modell der Kognition” at the international meeting “Konstruktivismus und Kognitionswissenschaft,” Wittgenstein-Haus, Vienna, 13 November 1996.

Horizontal dimension

Philosophical / Epistemological

The philosophical-epistemological version of constructivism is mainly represented by Ernst von Glasersfeld (EvG). He claims that knowledge is not passively received but actively built up by the cognizing subject (first principle of EvG). Furthermore the function of cognition is adaptive; it serves the organization of the experiential world, not the discovery of ontological reality (second principle). He calls his version “radical constructivism” because he claims that constructivism has to be applied to all levels of description. “Those who ... do not explicitly give up the notion that our conceptual constructions can or should in some way represent an independent, ‘objective’ reality, are still caught up in the traditional theory of knowledge.” (Quoted from his 1991 paper Knowing without Metaphysics.)

EvG refers to the skeptic tradition in philosophy, especially Sextus Empiricus, Berkeley (Esse est percipi, i.e., to be is to be perceived), Vico (Verum ipsum factum, i.e., the truth is the same as the made), and OttoVaihinger (The philosophy of the As-If). For EvG, skepticism points the way to the insight that whatever world view we construct we do not have any means to validate it He also quotes Jean Piaget from whom he takes over the idea that the child constructs his or her world by means of assimilation and accommodation.


Glasersfeld, E. von (1995) Radical Constructivism. A Way of Knowing and Learning. London: Falmer Press.


Originally hired as editor of the proceedings of the Macy-conferences on cybernetics (cf. also Pias 2003) the subject of which was “circular-causal and feedback mechanisms in biological and social systems,” it soon stroke Heinz von Foerster (HvF) that a “cybernetics of observing systems” is far more interesting than a “cybernetics of observed systems.” His so defined second-ordered cybernetics (SOS) became a motto of the Biological Computing Lab he was running for many years.

Starting from the insight that nervous signals are just electrochemical, Heinz von Foerster formulated the Principle of Undifferentiated Encoding: “The response of a nerve cell does not encode the physical nature of the agents that caused its response. Encoded is only ‘how much’ at this point on my body, but not ‘what’” (Foerster 1973/2003, pp. 214–215). The principle can be found in Maturana and Varela’s claim that the cognitive apparatus is an “organizationally closed system” (see biological constructivism).

Foerster distinguishes between trivial and non-trivial machines. The former maps input to output according a mapping-function without memory (i.e., corresponds to finite state machines with regular grammar). Non-trivial machines consist of a memory holding an internal state and two mapping functions. The “effect” function that maps input to output depending on the internal state. The “state” function performs the state transition depending on the input. Of course, Foerster’s classification is fully covered by the Chomsky hierachy of formal grammars but he uses his disnction to point out how difficult it is to deduce the structure of a non-trivial machine from its behavior.

Further concepts of Foerster are: trivialization, and eigenbehavior.

Many (first-order) cybernetic insights have been worked out by W. Ross Ashby.

Stuart Umpleby focuses on the application of SOS to social and economic problems.


Ashby, W. R. (1956) Introduction to Cybernetics. New York: Methuen. [pdf file of 1.9 MB]

Foerster, H. von (2003) Understanding Understanding. New York: Springer-Verlag. [Collection of papers that appeared in the 1960s and 1970s].

Pias, C. (ed) (2003) Cybernetics | Kybernetik. The Macy-Conferences 1946-1953. Volume 1 Transactions/Protokolle. Diaphanes: Zürich, Berlin.

Psychological / Cognitive

The developmental psychologist Jean Piaget became known for his statement “L’intelligence organise le monde en s’organisant elle-même.” In his theory of cognitive development (e.g., 1937/1954) he argued that in the beginning, a newborn knows little about how to cope with the perceptive impressions around her. Faces might be funny or threatening colorful spots and voices unknown sounds. In fact, she doesn’t even know that these are colors and sounds. Only by assimilation and accommodation the child constructs a collection of rules (schemata) during her ontogeny. Schemata serve as point of reference when it comes to assimilate new experiences. If impressions are too alien to be aligned to an older, already assimilated experience, they are either not perceived at all or give rise to the accommodation of those existing schemata, which are appropriately adjusted in order to include the new ‘exotic’ experience. With each of these assimilating or accommodating steps the child constructs another piece of reality. Piaget’s theory has been interpreted in a constructivist way especially by EvG.

Psychologist Ulric Neisser developed a theory of schemata controlled information pickup. A cognitive schema “accepts information as it becomes available at sensory surfaces and is changed by that information. It directs movements and exploratory activities that make more information available, by which it is further modified.”

For Kevin O’Regan and Alva Noë “seeing is knowing sensorimotor dependencies”, and the brain is a device to extract algebraic structures between perception and action. The authors refer to the work of Donald MacKay on “sensorimotor contingencies” and continued the work of Paul Bach-y-Rita (1972) who pioneered with work on sensory substitution. In particular, Bach-y-Rita showed how a blind person could gain some notion of sight by converting visual camera images into tactile information, and interpreted this as expression of brain plasticity.


Bach-y-Rita, P. (1972) Brain Mechanisms in Sensory Substitution. New York: Academic Press.

Neisser, U. (1976) Cognition and Reality. San Francisco: W. H. Freeman.

O’Regan, J. K. & Noë, A. (2001) What it is like to see: A sensorimotor theory of perceptual experience. Synthese 129 (2001): 79-103.

Piaget, J. (1937) La construction du réel chez l’enfant. Neuchâtel: Délachaux & Niestlé, 1937. Reprinted in Piaget, J. The Construction of Reality in the Child. New York: Ballantine, 1954.

Biological / Neurobiological

Biologists Humberto R. Maturana and Francisco J. Varela formulated the theory of autopoietic systems as a sub-class of self-organizing systems which, if they exist in the physical domain, are the class of living systems. For them, the nervous system is a closed network of interacting neurons where any change in the state of relative activity of a collection of neurons leads to a change in the state of relative activity of other or the same collection of neurons. This is referred to as the “organizational closure” of the nervous system. It represents the first principle of radical constructivism (Riegler 2001).

Neurophysiologist Rudolfo R. Llinás provides empirical backing. He too formulated a Closed-system Hypothesis: “[The brain] is capable of doing what it does without any sensory input whatsoever.” According to his dreaming machine-argument, we “are basically dreaming machines that construct virtual models of the real world.”

Neurophysiologist Gerhard Roth (Haynes et al. 1998) maintains that the limbic system, the unconsciously working part of the brain responsible for evaluations, is the ultimate instance of volitional cognition. In their view, consciousness is just a pseudo-ruling ego. It is not the ego who constructs; it is constructed. (For additional arguments and consequences see Riegler 2003).


Haynes, J.-D., Roth, G., Schwegler, H. & Stadler, M. (1998) Die funktionale Rolle des bewußt Erlebten. [The functional role of conscious experience].”Gestalt Theory 20: 186-213.

Llinás, R. R. (2001) I of the Vortex. Cambridge: MIT Press.

Maturana, H. & Varlea, F. (1980) Autopoiesis and Cognition: The Realization of the Living. Boston Studies in the Philosophy of Sciences. Vol. 42. Boston, Dordrecht: D. Reidel.

Riegler, A. (2001) Towards a Radical Constructivist Understanding of Science. Foundations of Science 6(1-3): 1-30.

Riegler, A. (2003 ) Whose anticipations? In Anticipatory Behavior in Adaptive Learning Systems: Foundations, Theories, and Systems, Lecture Notes in Artificial Intelligence, edited by M. Butz, O. Sigaud, and P. Gérard. New York: Springer-Verlag, pp. 11-22.


For physicist Olaf Diettrich, perceived patterns and regularities are just invariants of inborn cognitive (sensory) operators. Therefore, laws of nature are human-specific. A different set of cognitive operators yields a different cognitive phenotype. Creatures equipped with such alternative phenotypes would be impossible to communicate with. Diettrich’s approach also claims a homology between mechanisms generating mathematical terms and those generating observational ones, explaining thus why mathematics is such an effective tool to describe the world.

Physicist Gerhard Grössing maintains that perceived non-classical structure of space and time in relativistic cases are human-specific artifact based on neurophysiological processes.


Diettrich, O. (2001) A Physical Approach to the Construction of Cognition and to Cognitive Evolution. Foundation of Science 6 (4): 273-341.

Grössing, G. (2001) Comparing the Long-Term Evolution of “Cognitive Invariances” in Physics with a Dynamics in States of Consciousness. Foundation of Science 6 (4): 255-272.

Psychiatrist / Therapeutic

Paul Watzlawick’s well-known Palo-Alto group for family therapy uses constructivism to make patients solve their interpersonal problems. The basic therapeutic intervention is to disrupt pattern of symptomatic interaction by “reframing” a habitual situation, i.e., to “place conceptual and/or emotional setting or viewpoint in another frame which fits the ‘facts’ of the same concrete situation equally well or even better and thereby changes its entire meaning.” This encourages the patients to find alternative constructions of their worldview.

Psychologist George Kelly became famous for his statement “A person’s processes are psychologically channelized by the way in which he anticipates events.” He is the founder of Personal Construct Psychology.


Kelly, G. (1963) A Theory of Personality. New York: Norton.

Watzlawick, P., Weakland, J. & Fisch, R. (1974) Change: Principles of Problem Formation and Problem Resolution. New York: W. W. Norton.

Literature / Media Sciences

Literature scientist Siegfried J. Schmidt (SJS) introduced radical constructivism in media science in the 1980s and made thereby RC known and popular in the German-speaking countries. Part of the merits go also to Wolfram K. Köck who made excellent German translations of constructivist authors such as Maturana, Glasersfeld, and Foerster.

Further researchers in this area are Gebhard Rusch, Nancy Spivey, Tötösy de Zeptenek, and Stefan Weber who applies constructivism to journalism.


Rusch, G. (1987) Erkenntnis, Wissenschaft, Geschichte. Frankfurt: Suhrkamp.

Schmidt, S.J. (ed.) (1987) Der Diskurs des Radikalen Konstruktivismus. Suhrkamp: Frankfurt a. M.

Spivey, N. N. (1997) The Constructivist Metaphor. Reading, Writing, and the Making of Meaning. San Diego: Academic Press.


Proponents of a computational constructivism are Steven Quartz, and Gert Westermann.


Quartz, S. & Sejnowski, T.J. (1997) The neural basis of cognitive development: A constructivist manifesto. Behavioral and Brain Sciences 20 (4): 537-596.

Westermann, G. (2000) Constructivist Neural Network Models of Cognitive Development PhD thesis at the University of Edinburgh.


Claims that (scientific) knowledge does not arise within cognizing individuals or within nature but is socially constituted. Proponents are Kenneth Gergen, Bruno Latour, Karin Knorr Cetina, and Dirk Baecker.


Knorr-Cetina, K. (1981) The Manufacture of Knowledge: An Essay on the Constructivist and Contextual Nature of Science. Oxford: Pergamon Press.

Latour, B. (1987) Science in Action. Cambridge: Harvard University Press.

System Theoretical

Building primarily on Maturana and Varela’s autopoietic theory, Niklas Luhmann developed a system theoretical version of constructivism, which has found many followers especially in Germany.


Ernst von Glasersfeld, Leslie Steffe, as well as Paul Ernest contributed a great deal to implementing radical constructivism in educational sciences. Former BCL member Gordon Pask developed a constructivist theory of communication with application to education.

Vertical dimension

Regardless of their disciplinary background, all variants of constructivism are subject to the decision of how thoroughly thy ant to apply the constructivist thought. Following Ernst von Glasersfeld, we can distinguish the following two levels.

Trivial (or modest constructivism)

Here, differently constructed worldviews gradually converge towards a knowledge system that represents the world objectively.

Radical (or meta-constructivism)

Constructivism must strive for completeness, i.e., being radical with its claim to uncompromisingly apply the idea of constructions on all levels.

Common Ground: The Four Postulates of RC

From the many variations of radical constructivism I propose the following four postulates as its common ground. For more details check my paper Towards a Radical Constructivist Understanding of Science. Foundations of Science 6(1-3): 1-30, 2001, and other publications mentioned above.

1 Radical Constructivist Postulate

The nervous system is organizationally closed.

2 Epistemological Corollary

We can neither confirm nor reject an external absolute reality. Therefore, RC avoids the extremes of realism and solipsism. Representation is not the mapping of external entities onto cognitive structures but is system-relative.

3 Methodological Corollary

Knowledge is circular but non-tautological. Instead of using reality as point of reference, the coherence and consistency of belief systems are emphasized.

4 Limitation of Construction Postulate

As cognition is implemented in form of a hierarchical interdependent network, mutual interdependencies among its consituents make an “Anything Goes” impossible. Also there are different levels of changeability of constructions, depending on their degree of linkage with other and especially older components.


That constructivism does not have a common ancestor can be derived from the fact that many researchers and philosophers developed their respective versions without having paid attention to historical or contemporary parallels. Hence they introduced their insights under a variety of labels. Here is a (most likely incomplete) list of constructivist theories.

Biology of Cognition

Humberto Maturana and Francisco Varela provided a biologically justified embedding of reality in actuality. It is based on the idea that living beings are autopoietic systems (see biological constructivism).

Second Order Cybernetics

Mainly developed by Heinz von Foerster and W. Ross Ashby, it is based on the idea to apply cybernetics to observing systems (see cybernetic constructivism).

Constructivist Evolutionary Epistemology

Introduced by Olaf Diettrich, the CEE states that regularities on which laws of nature are based are invariants of inborn cognitive operators (see physical constructivism).

Theory of Sensorimotor Contingencies

Based on Donald MacKay’s concept, Kevin O’Regan and Alva Noë developed the concept of sensorimotor contingencies further (see cognitive constructivism).

Further Constructivisms

Theories which share the name but which are not necessarily compatible with the variants of constructivism mentioned above are listed here.

Constructive Realism

Its goal is the explication of scientific praxis and has been proposed by Friedrich Wallner and Gerard de Zeeuw.

Mathematical Constructivism

In reaction to mathematical Platonism, mathematical constructivists such as L.E.J. Brouwer, Arend Heyting, and Jean Paul van Bendegem claim that mathematical objects exist only if a method can construct them. As a consequence they oppose, for example, the notion of infinity.

Erlangen Constructivism

Paul Lorenzen and Wilhelm Kamlah attempted a circular-free foundation of sciences and scientific languages. Its basis is twofold: a pre-scientific vocabulary and standardized action schemata to generate objects. Later, the Erlanger Constructivism has been transformed into the Methodological Culturalism by Peter Janich. He claims a relativism on the fact that all justifications are based on pre-active and pre-discursive consensuses, which are marked by the already achieved cultural level. (“Alle Begründungen und Rechtfertigungen finden zulässige Anfänge in präaktiven und prädiskursiven Konsensen, die durch eine schon erreichte Kulturhöhe ausgezeichnet sind.”)


Kamlah, W. & Lorenzen, P. (1967) Logische Propädeutik. Vorschule des vernünftigen Redens. Mannheim.

Zitterbarth, W. (1981) Der Erlanger Konstruktivismus in seiner Beziehung zum Konstruktiven Realismus. In: Peschl, M. F. (ed.) (1991) Formen des Konstruktivismus in Diskussion. Wien: WUV–Universitätsverlag, pp. 73–87.


Constructionism as an educational philosophy emphasizes that in order to learn about abstract concepts it is necessary to create and experiment with artifacts. In this perspective, understanding and experience are closely related in the sense that learning is considered a process of active knowledge construction rather than passive knowledge absorption.


Harel, I. and Papert, S. (eds.) (1991) Constructionism. Norwood: Ablex.

Russian Constructivism

This is a Russian painting style of the early 20th century.

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