philosophy is for everyone
and not just philosophers

philosophers should know lots
of things besides philosophy

Feature articles

PhiloSophos knowledge base

Philosophical Connections

Pathways to Philosophy programs

University of London BA

Pathways web sites

Philosophy lovers gallery

GVKlempner: complete videos

PhiloSophos home

Pathways to Philosophy

A Brief Outline of Radical Constructivism

by Nick Redfern

Indeed, there has never been nor will there ever be a man, Who knows the truth about the gods and all the matters of which I speak. For even if one should happen to speak what is the case especially well, Still he himself would not know it. But belief occurs in all matters.

Xenophanes of Colophon

1. Introduction

In his critical commentary on Richard Rorty, Pietersen (2005) identifies 'two main camps' in the history of philosophical thought, which he claims are 'indispensable' and 'complimentary,' and present us with 'the ancient, ongoing and seemingly unbridgeable divide between thinkers.' These two camps are the 'philosophies of the One,' which are understood to be broadly Platonic; and the 'philosophies of the Many,' which he associates with Sophism. For Pietersen, this divide is unavoidable:

There seems to be no escaping this dialectic. One cannot go further, there is no Hegelian synthesis into 'Absolute Spirit' here — only the possible danger of disappearing into a 'cloud of all-knowing' (dogmatism, foundationalism, a mystical One) or a 'morass of never-knowing' (scepticism, relativism, a mere passing parade of the Many). That is why, [in Pietersen's view], the centre must be made to hold -- why both centrifugal and centripetal forces are needed in human thought.

It is essential, in Pietersen's view, to avoid the extremes of the determinism and the totalitarianism of the 'Rule of the One' and the anarchism of the 'Rule of the Many' by maintaining a dialogue between these two opposing philosophies.

However, there is no reason why philosophy should be confined to these opposing positions, or why we should carry on this dialogue. In this essay I outline Ernst von Glasersfeld's Radical Constructivism as a theory of knowing that does not conform to Pietersen's description of the conversation of philosophy. It is to be distinguished from both realism and solipsism, and offers the possibility of moving beyond an exhausting and exhausted debate.

2. Radical Constructivism

Searle (1999: 2079) states that, 'the biggest single obstacle to progress of a systematic theoretical kind has been the obsession with epistemology.' Radical Constructivism is an attempt to move beyond epistemology, and has been described by the school's founder, Ernst von Glasersfeld (1984, 1991, 1995), as a 'theory of knowing' rather than a 'theory of knowledge.'

Radical Constructivism was conceived as an attempt to circumvent the paradox of traditional epistemology that springs from a perennial assumption that is inextricably knitted into Western philosophy: the assumption that knowledge may be called 'true' only if it can be considered a more or less accurate representation of a world that exists 'in itself,' prior to and independent of the knower's experience of it. The paradox arises, because the works of philosophers by and large imply, if not explicitly claim, that they embody a path towards Truth and True representations of the world, yet none of them has been able to provide a feasible test for the accuracy of such representations (Glasersfeld 1991: 13).

As such an approach, Radical Constructivism has been described as 'post-epistemology' (Noddings 1990). Radical Constructivism puts forward two main claims:

knowledge is not passively received but actively built up by the cognising subject; the function of cognition is adaptive and serves the organisation of the experiential world, not the discovery of ontological reality (Glasersfeld 1989: 162).

From a Radical Constructivist perspective, the cognising subject cannot transcend his/ her experiences and all knowledge is constructed out of those experiences. However, this does not imply a denial of reality, but states that as we cannot transcend the limits of our experience it is impossible to tell (and therefore unnecessary to know) to what degree our knowledge reflects an observer-independent reality. Consider Sextus Empiricus' example of the cognising organism's experience of an apple:

Each appearance that we perceive through the senses seems to present itself under many forms; an apple, for instance, seems smooth, fragrant, sweet, and yellow. It is uncertain, however, whether these are really the only qualities it possesses, or whether it is of one quality only but appears in different forms because the various sense-organs are of different construction. It may also be that it has more qualities than are apparent, and that some of them are not perceived by us... there may subsist in the apple only those qualities which we seem to apprehend, likewise that there may subsist more than just these; or again that even the ones we perceive may not subsist at all; it follows that it will be non-evident to us what kind thing the apple is (Sextus Empiricus 1985: 57-59).

Note that Sextus Empiricus states that our experience of an apple is neither absolutist nor relativistic, but is 'uncertain.' That is, any cognising organism that experiences an apple cannot claim to possess knowledge because there can be no way of confirming or denying to what extent its experiences represent reality. From this perspective both ontology and epistemology are redundant: Radical Constructivism is agnostic with regard to whatever may 'exist,' and it is important to note that Radical Constructivism is a theory of knowing and not a theory of being.

In the place of representing the 'real' world, Radical Constructivism identifies a different function for cognition in organising the cognising organism's experiential world. This aspect is derived from the work of Jean Piaget (1937), who stated that: 'The essential functions of the mind consist in understanding and in inventing, in other words, in building up structures by structuring reality (Piaget 1971: 27). As a biologist, Piaget described the process organising experience as a process of adaptation, in which a cognising organism seeks to assimilate its experiences into the psychological structures it already possess and where it is unable to do so attempts to accommodate the error by modifying those structures or creating new ones. Glasersfeld (2001: 39) describes the principle of adaptation in Radical Constructivist thought:

[A]daptation is not an activity but the result of the elimination of all that is not adapted. Consequently, on the biological level, anything that manages to survive is 'adapted' to the environment in which it happens to find itself living... Taken out of the biological context and applied to cognition, this means that 'to know' is not to possess true representations of reality, but rather to possess ways and means of acting and thinking that will allow one to attain the goals one happens to have chosen.

The key to evaluating competing knowledge claims, therefore, is not to seek to compare them to a mind-independent reality that cannot be known, but to assess their cognitive viability. There is more at stake here than the 'conversation of philosophy:' our very survival is dependent upon us possessing viable ways and means behaving in the world.

The principle of adaptation allows us to avoid the anarchistic relativism of the 'philosophies of the Many' by accepting that a cognising organism is constrained by its environment and its historical assembly. The environment, as it is experienced by an organism, is experienced as a set of constraints.

Riegler (2001) cites the example of a traffic network consisting of different means of transportation. If we travel by car, then only those points connected by roads are accessible; whereas if we travel by foot, those points that lie in between may be accessed but only if they are within walking distance. The different modes of transportation impose different restrictions on our ability to move about the network, and so 'free arbitrariness ' is not possible. The decision to take a particular mode of transport will act as a constraint on our subsequent decisions about where we are going and how quickly we get there.

Similarly, the construction network is the mind is necessarily non-arbitrary, and Riegler describes constructions as historical assemblies. This historical aspect imposes a hierarchical organisation in which more recent additions build on older ones, creating mutual interdependencies between an organism's experiences and severely restricting the degrees of freedom of the way subsequent constructions can be accomplished. Furthermore, the action of cognising organisms is goal-directed, and successful actions will be repeated because such organisms are inductive and function in a conservative manner in so far as they repeat only that which works (Maturana 1970). Note that Radical Constructivism does not deny that a cognising organism interacts with its environment but does deny that such an organism can know reality in the traditional, ontological sense: the environment that we experience is always our construction (Foerster 1973). Radical Constructivism does not limit us to the absolutism of the 'philosophies of the One,' but equally it does not permit that 'anything-goes.'

3. Conclusion

Pietersen's division of philosophy into categories of 'the One' and 'the Many' only maintains its relevance within a traditional approach to knowledge. It is an antiquated debate, but unfortunately one that shows no signs of flagging. Since Xenophanes stated that all man could have is belief, the arguments of the sceptics have been rejected by those who claim knowledge of the world, but in 2500 years of Western philosophy it has never been demonstrated how it is possible for a cognising organism to know the world. Yet the dogmatic belief in realism persists.

The argument that it is a virtue to keep the conversation between these differing philosophies is noble, but ignores the fact that these positions increasingly become polarised over time. Philosophers on both sides of this ancient divide do not engage in constructive discourse; rather, they talk past one another. Dr. Johnson's refutation of Bishop Berkeley's A Treatise Concerning the Principles of Human Knowledge could hardly be described as sincere or useful debate. Radical Constructivism is an approach that affords the philosopher an escape from Pietersen's unending dialectic, and offers a non-traditional approach to philosophy that allows us to be free of an ancient philosophical debate that ultimately cannot be resolved, and to develop new ways of understanding how and why we make sense of the world in the way we do. As La Moigne (1995) has pointed out, constructivism is a theory that requires philosophers to make a radical break from the generally accepted view that our knowledge of the world must lie somewhere between materialism and idealism.


Foerster, H. von, On constructing a reality, in F.E. Preiser (ed.) Environmental Research Design, Volume 2. Stroudsburg: Dowden, Hutchinson & Ross, 1973: 35-46.

Glasersfeld, E. von (1984) An introduction to radical constructivism, in P. Watzlawick (ed.) The Invented Reality: How Do We Know What We Believe We Know? New York: Norton: 17-40.

Glasersfeld, E. von (1989) Constructivism in education, in T. Husen and T. Neville Postlethwaite (eds.) The International Encyclopaedia of Education Research and Studies: Supplementary Volume 1. Oxford: Pergamon Press: 162-163.

Glasersfeld, E. von (1991) Knowing without metaphysics: aspects of the radical constructivist position, in F. Steier (ed.) Research and Reflexivity. London: Sage: 12-29.

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

Glasersfeld, E. von (2001) The radical constructivist view of science, Foundations of Science 6 (1-3): 31-43.

La Moigne, J-L. (1995) Les epistemologies constructivistes. Paris: Presses Universitaires de France.

Maturana, H. (1970) Biology of Cognition: Biological Computer Laboratory Research Report BCL 9.0. Urbana: University of Illinois.

Noddings, N. (1990) Constructivism in mathematics education, in R. B. Davis, C. A. Maher, and N. Noddings (eds.) Monographs of the Journal for Research in Mathematics Education 4. Reston, VA: National Council of Teachers of Mathematics: 7-17.

Piaget, J. (1937) La construction du reel chez l'enfant. Neuchatel: Delachaux et Niestle.

Piaget, J. (1971) Science of Education and the Psychology of the Child. New York: Viking Press.

Pietersen, H.J. (2005) Critical commentary on Richard Rorty's thought, Philosophy Pathways 111.

Riegler, A. (2001) Towards a radical constructivist understanding of science, Foundations of Science 6 (1-3): 1-30.

Searle, J.R. (1999) The future of philosophy, Philosophical Transactions: Biological Sciences 354 (1392): 2069-2080.

Sextus Empiricus (1985) Selections from the Major Writings on Scepticism, Man, and God, edited by P.P. Hallie and translated by S.G. Etheridge. Indianapolis: Hackett Publishing Company.

© Nick Redfern 2005