Abstract
The current faddish use of the term constructivism has taken on as many different definitions as the number of people attempting to define it. This essay clarifies the meaning of constructivism through an examination of Karl Popper's and Jean Piaget's theories. The authors provide a rationale for the use of Popper's paradigm of “Three Worlds” and how his criterion for open and closed theories serves as a framework for Piaget's constructivist theory.