A major concern is to demonstrate the contradictory nature of Maturana’s conception of ontology. A realist view of the external world is presented, assuming that the independence of the common-sense and scientific entities of the world from our schemes of representation does not render the world an ineffable, inaccessible realm of unspecifiable objects. The theory of Maturana is examined in details with regard to a possible philosophical interpretation, concluding that though Maturana describes himself as presenting a doctrine free of all ontological commitments, that self-description is false.

I assume that every theory of knowing presupposes an ontology or metaphysics, identifying the organization of beings capable of knowing something and the domain of objects and relations to which their knowledge claims might apply. Constructivist epistemology will be no exception. In particular, Ernst von Glaserfeld’s “radical” constructivism and Humberto Maturana’s “bringforthist” position incline toward metaphysical idealism, as both theories overstate the antirealist implications of a trivially true version of perspectivalism. My outline of hypothetical realism is designed to highlight several constructivist misconceptions, including: (1) the idea that there can be no meaningful access to a world that exists and has a nature independently of our making; (2) the idea that constructivism alone recognizes the irreducible plurality of our perspectives on the world; and (3) the idea that constructivist anti-realism is compatible with a focus on the social or linguistic nature of experience.

In this paper I identify five logical fault lines in Ernst von Glasersfeld’s exposition and defense of radical constructivism (RC). Ordered, roughly, from the epistemological-metaphysical to the social-political-educational, the five are as follows: (1) that the constructive nature of the knowing process necessarily restricts in some important way that which can be known; in particular, (2) that we cannot know (on any non-mysterious interpretation of the word “know”) the metaphysical realist’s mind – or language – independent objects of knowledge; (3) that RC is an ontologically neutral doctrine, resting somewhere beyond the dispute between metaphysical realism and idealism; (4) that RC is compatible with a focus on the social or linguistic nature of experience; and, finally, (5) that RC is an inherently progressive or tolerant theory.

Context: Few professional philosophers have addressed in any detail radical constructivism, but have focused instead on the related assumptions and limitations of postmodern epistemology, various anti-realisms, and subjective relativism. Problem: In an attempt to supply a philosophical answer to the guest editors’ question, “Why isn’t everyone a radical constructivist?” I address the realist (hence non-radical) implications of the theory’s invocation of “others” as an invariable, observer-independent, “external” constraint. Results: I argue that constructivists cannot consistently defend a radically subjectivist theory of knowing while remaining entirely agnostic about the nature and existence of the larger world (including independent others). That is, any non-solipsistic account of human experience must explicitly acknowledge its extra-subjective, ontological dimension. Implications: It follows that no pedagogical, social, philosophical, or commonsensical insight associated with so-called “trivial” or “social” constructivism survives or receives any support from the move to radical constructivism.

Key words: Ernst von Glasersfeld, solipsism, fictional posits, ontological agnosticism, others, subjects, observer-independence

(from the back cover): “Do our thoughts and claims about the world give us rational access to the way the world really is? Can subjective experience ever provide a basis for grasping objective truth? These perennial questions of philosophy reach to the heart of every human endeavor, from education to science to everyday, successful practice. Despite the intuitive and nearly universal appeal of realism, influential thinkers from many fields – including educational theory, psychology, cybernetics, literary criticism, biology, and physics – have long followed the skeptics in denying knowers any kind of reliable bridge to the world. This volume offers the first comprehensive assessment and critique of radical constructivism, a famously skeptical theory of knowledge with a large following across the academic disciplines. Employing a dialogic mode of discourse, the authors have crafted an accessible and concise treatise that both details the solipsistic perils of antirealism and defends an alternative, constructivist realist account of our place as knowers in the larger, constraining world.”

Excerpt: Clifford Geertz (1983) speaks of “genre blurring” to refer to, among other things, the cross-fertilization of the social sciences and the humanities. In the process, the social sciences are giving up their long-held objective of patterning themselves after the physical sciences. This volume might be looked at as a case study of such genre blurring. Some of the contributors come from academic backgrounds other than mathematics and mathematics education. They include academics trained in psychology, philosophy, and classical studies. This diversity is reflected to some extent in the lack of overlap in the works each chapter references. But there is a stronger rationale for characterizing these chapters as cross-disciplinary: one finds within single chapters, references culled from a variety of disciplines. Although the authors come from and draw on diverse disciplines, they share a core perspective. This shared perspective is a species of constructivism. There are many possible tacks to take in an introductory chapter such as this. What seems the most appropriate in this case is to orient the reader who is interested in mathematics education, for example, but who may be unaware of constructivist epistemology. Accordingly, we describe general philosophical and psychological issues that underlie the constructivism advocated by these authors. Having done this, we provide a brief overview of the volume in which we highlight the primary focus of each chapter.