2000, Donald Kiraly, A Social Constructivist Approach to Translator Education, St. Jerome Publishing, p. 18:There is no single theory of constructivism. In fact, there are many shades and varieties of constructivism spanning a range of perspectives. There is also no single individual who can be identified as the founder of constructivism. In fact, rather than tracing a linear development along one line of philosophical thought, constructivism seems to circumscribe a set of thinkers, theories and approaches that spring from a plethora of historical and cultural origins.
2001, George J. Klir, Facets of Systems Science, According to constructivism, all systems are artificial abstractions. They are not made by nature and presented to use to be discovered, but we construct them by our perceptual and mental capabilities with the domain of our experiences.