Jakob von Uexküll is mostly known for his concept of Umwelt – the meaningful surrounding of animals. von Uexküll insisted vehemently on the fact that Umwelt vindicated Kant’s subjectivist epistemology in the biological domain. However, we argue that a crucial yet widely overlooked development in von Uexküll’s theory of meaning implies a more radical vision strikingly germane to J. J. Gibson’s own direct realist epistemology-ontology and in tension with his own subjectivist concept of Umwelt. Gibson argued that organism and environment are complementary and meaning is not constructed via a subjective act but is directly available in the world as opportunities for action, namely, affordances. We show that von Uexküll’s notion of “functional tone” is similar to Gibson’s concept of affordance in that it includes action in perception. More important, von Uexküll introduces the musical metaphor of harmony to characterize the relationship between animal and environment. Like Gibson’s reciprocity, harmony implies an unmediated isomorphism between the dispositions of the animal and those of the environment that allows for direct perceptual contact with the world and action upon it.

Open peer commentary on the article “Going Beyond Theory: Constructivism and Empirical Phenomenology” by Urban Kordeš. Upshot: A constructivist epistemology might help us better understand what kind of knowledge expert introspection cannot deliver. Indeed, there are well-known trade-offs with regard to the insights that can be gained through introspection. If trivialization is to be avoided, then it should be assumed that, contrary to standard science, introspection just is not a declarative kind of knowledge.

Open peer commentary on the article “Applying Radical Constructivism to Machine Learning: A Pilot Study in Assistive Robotics” by Markus Nowak, Claudio Castellini & Carlo Massironi. Upshot: I argue that the authors miss an important distinction between realism and representationalism. Because of this, their diagnosis of the current state of machine learning is valid, but for the wrong reasons. As a consequence, their approach to upper limb prosthetics may not be a step in the right direction.

Upshot: Gibsonian and enactivist thinkers appear to diverge primarily with respect to the emphasis placed on the contributions of the organism to perception-action. Enactivists claim that a fundamental asymmetry in the organism-environment relationship should be credited for the existence of meaning in the world. Gibsonians counter that theory must reckon with both the asymmetry and symmetry between organism and environment as well as with the role of specificational information in underwriting their coordination.

Context: The dominant approach to the study of perception is representational/computational, with an emphasis on the achievements of the brain and the nervous system, which are taken to construct internal models of the world. Alternatives include ecological, embedded, embodied, and enactivist approaches, all of which emphasize the centrality of action in understanding perception. Problem: Despite sharing many theoretical commitments that lead to a rejection of the classical approach, the alternatives are characterized by important contrasts and points of divergence. Here we focus on the enactive and ecological approaches, in particular, on how they construe the status of the environment and the content of perception. Method: We begin with a review of James Gibson’s ecological psychology, highlighting it as a psychology for all organisms not just humans. Against this backdrop, we consider enactivist arguments against direct perception - a central assertion of the ecological approach - and in favor of interpreting the activity of perceptual agents as a kind of construction of a perceptually meaningful world. Results: We assess the merits of this interpretation and we conclude that it cannot be grounded on fundamental principles such as thermodynamics and organism-environment mutuality. Implications: As a consequence, enactivism remains close to representationalism and entails a form of dualism. Constructivist content: We advance a criticism of the constructivist foundations of the enactive approach to perception. Perception-action mutuality at the heart of enactivism does not require mental construction; indeed, perception-action mutuality obviates construction.

Key words: Ecological psychology, Gibson, constructivism, enactivism, perception, representation.