According to Ernst von Glasersfeld, our resident philosopher and expert on constructivism:
Constructivism was introduced in the modern era by Jean Piaget as a way of thinking about cognition and knowledge, not as a metaphysical theory about what might exist.
It's fundamental tenet is: The mind organizes the world by organizing itself (Piaget 1937).
The "radical" version of constructivism was developed independently by Heinz von Foerster (1981) and Ernst von Glasersfeld (1984). Knowledge, from this perspective, is not a representation of "objective" facts, but a compendium of concepts, conceptual relationships, and rules that have proven useful in domesticating our experiential world.
Foerster, H. von (1981) Observing systems. Seaside, California: Intersystems Publications.
Glasersfeld, E. von (1984) An introduction to radical constructivism, in P. Watzlawick (ed.) The invented reality. New York: Norton. German original, 1981.
Piaget, J. (1971) The construction of reality in the child; New York: Basic Books. French original, 1937.
For a great deal more about radical constructivism — both more extensive and more authoritative than we can provide here — we direct you to the extensive writings on the Radical Constructivism web site.
(The essay that follows is lacking in "scholarly" background, citations, etc. The reason is that it was pulled out of a very specific context. We present it here in the spirit of "perhaps you will find it useful.")
Constructivism and Science Education
In what way is a constructivist view of science education different from other views? The answer lies in the tenets of constructivist philosophy, which assert that all knowledge is constructed as a result of cognitive processes within the human mind. While this may appear to be a harmless enough statement, many find (so-called) radical constructivism somewhat unpalatable.