A widely cited roadblock to bridging ecological psychology and enactivism is that the former identifies with realism and the latter identifies with constructivism, which critics charge is subjectivist. A pragmatic reading, however, suggests non-mental forms of constructivism that simultaneously fit core tenets of enactivism and ecological realism. After advancing a pragmatic version of enactive constructivism that does not obviate realism, I reinforce the position with an empirical illustration: Physarum polycephalum, a communal unicellular organism that leaves slime trails that form chemical barriers that it avoids in foraging explorations. Here, environmental building and sensorimotor engagement are part of the same process with P. polycephalum coordinating around self-created, affordance-bearing geographies, which nonetheless exist independently in ways described by ecological realists. For ecological psychologists, affordances are values, meaning values are external to the perceiver. I argue that agent-enacted values have the same status and thus do not obviate ecological realism or generate subjectivism. The constructivist-realist debate organizes around the emphasis that enactivists and ecological theorists respectively place on the inner constitution of organisms vs. the structure of environments. Building on alimentary themes introduced in the P. polycephalum example and also in Gibson’s work, I go on to consider how environment, brain, visceral systems, and even bacteria within them enter perceptual loops. This highlights almost unfathomable degrees of mutually modulating internal and external synchronization. It also shows instances in which internal conditions alter worldly configurations and invert values, in Gibson’s sense of the term, albeit without implying subjectivism. My aim is to cut across the somatic focus of enactive constructivism and the external environment-oriented emphasis of ecological realism and show that enactivism can enrich ecological accounts of value.

Key words: affect and value, central and peripheral nervous system, ecological psychology, enactivism, gut microbiome, pragmatism and phenomenology, physarum polycephalum, realism vs. constructivism.

Context: In the literature concerning the theory of social systems, interest in epistemological and ontological questions has increased in recent years. The controversies regarding a realist vs. constructivist interpretation of Luhmann’s theory, as well as the concept of many realities that correspond to many ontologies, deserve attention. Problem: The paper discusses interrelated ontological and epistemological problems in Luhmann’s systems theory, such as ontology and de-ontologization, realism vs. constructivism, contingency and its limits and one vs. many realities. Method: The paper proposes an interpretation, according to which systems theory is based on an epistemology - radical operative constructivism. Results: Luhmann is not a realist. The last word belongs to radical operative constructivism, and naïve realism with reference to social systems has only a preliminary, methodological significance. However, taking a position in the dispute between realism and constructivism inevitably involves an ontological “vocabulary,” that is, usage of the reality/construction distinction. Furthermore, operative constructivism formulates the necessary conditions of the possibility of cognition, which limit the contingency of the theory and constitute one reality that is a construction of systems theory. Luhmann rejects ontology, but he does not renounce epistemology, and consequently the project of de-ontologization remains incomplete. Implications: The paper offers a new, coherent interpretation of ontological and epistemological questions in Luhmann’s theory, and also throws light on some problems of radical constructivism in general, such as the ontological implications of epistemology or the constructivist self-reference of theories. Key words: Radical operative constructivism, social systems, Luhmann, ontology, reality, contingency.