Enacting Worlds

A living thing does not simply confront a world that is already divided into meaningful features. Its activities arise from a particular way of living, with particular ways of maintaining itself, moving, sensing, and acting. A chemical gradient can matter to a bacterium because it bears on conditions for continued activity; a surface can matter to an animal because it can be climbed, grasped, or avoided; the movement of another individual can matter because it offers possibilities for approach, escape, or interaction.

We can describe features of the surroundings, measure what an organism detects, and explain how those detections affect behavior. What does it mean to say that a feature of the surroundings is significant for the living thing itself? From an enactive perspective, such significance emerges in relation to the organization and activity of the living system rather than sitting in the surroundings waiting to be detected. This is part of what enactivists mean by sense-making (Thompson, 2007).

This point does not depend on assuming that every living thing has the same kind of subjective experience. A bacterium can respond selectively to conditions that support or disrupt its continued activity without our needing to say what, if anything, it feels like to be a bacterium. In animals, the relations among embodiment, action, significance, and experience become richer and more difficult to separate. What is common across these cases is that interactions are not equivalent from the standpoint of the living system. Its organization and history help establish what can make a difference and what it can do in response.

An older idea that helps here is Jakob von Uexküll’s concept of the Umwelt (Uexküll, 2010; see also Brentari, 2015). Uexküll asked us to understand an animal as a subject living in its own world rather than simply as an object moving through surroundings defined by a human observer. Its Umwelt is shaped by relations between perception and action within a particular way of life. His famous example is the tick (Uexküll, 2010). In Uexküll’s account, after mating the female tick climbs vegetation, guided by a general sensitivity to light, and waits. The odor of butyric acid associated with a passing mammal prompts her to let go. If she lands on something warm, she crawls across it and uses touch to find a relatively hairless patch of skin, which she pierces in order to feed on blood. If she falls onto something cold, she has missed a suitable host and climbs back to a waiting place. After feeding, she eventually drops to the ground, lays her eggs, and dies. Uexküll’s description is a deliberately simple account of the animal’s behavioral world, not a complete modern account of tick host-seeking.

As with the bacterium moving toward sugar, mechanistic and evolutionary accounts can each explain the tick’s behavior without settling what it means to say that these particular cues, rather than countless other physical features of the surroundings, belong to the tick’s perceptual-action world.

Uexküll’s construct of the Umwelt concerns the meaningful world of an animal subject. Enactivism places this problem within a broader account of living organization and activity and takes up the further problem of how we should understand the claim that some interactions have significance for a living system.

Maturana’s notion of a cognitive domain concerns the interactions in which a living system can participate while maintaining its organization (Maturana & Varela, 1980). Later enactive work develops the idea of sense-making to describe how interactions acquire significance in relation to a system’s own organization and way of life. Across these traditions, embodiment means more than having a physical body or a set of sensory receptors. Perception and action belong to an organized way of living through which some features of the surroundings can matter while others do not.

Reflecting on Other Worlds

For humans, the world that becomes available through perception and action is likewise shaped by a specifically human form of embodiment. We see only a limited range of wavelengths, hear only a limited range of frequencies, and act with bodies that have particular scales, movements, and capacities. Other animals are differently equipped. Bees can detect ultraviolet patterns on flowers, many birds can perceive wavelengths that humans cannot, and mosquitoes can detect chemical information through sensory receptors on their legs and other body parts. These differences matter, but an Umwelt is more than a list of sensory abilities: what counts is how perception and action are joined within the activities of a particular form of life.

Biology, neuroscience, and comparative psychology investigate other living things from a human scientific perspective. We can measure sensory ranges, describe nervous systems, record behavior, and manipulate features of the surroundings, and these methods can tell us a great deal. What they cannot give us directly is the animal’s own perspective on those relations. We can therefore learn about the conditions under which another animal perceives and acts without assuming that we thereby know what its world is like from the inside.

The collective activity of science nevertheless allows humans to move beyond the limits of unaided perception. Instruments and theories reveal wavelengths we cannot see, frequencies we cannot hear, microscopic structures, chemical processes, and many other features of the physical world. In this sense, different living things participate in a shared material world with regularities that do not depend on any one species perceiving them. But the metaphor of each species receiving a different “slice” of that world can also mislead if it suggests that perception simply samples a predivided set of neutral features. From an enactive perspective, what becomes relevant depends on the relation between the living system and its surroundings. The same physical feature can be significant in one form of life and irrelevant in another.

An enacted world is constrained by surroundings that the living thing does not invent. Its activity is shaped by material conditions, by its own organization, and by its history of interaction. A bacterium cannot make any chemical into a nutrient simply by treating it as one, and an animal cannot perceive wavelengths for which it has no relevant sensory capacities. At the same time, a nutrient is not meaningful as food merely because a particular molecule exists, and a surface is not climbable or graspable independently of the capacities of the living thing encountering it. A meaningful environment is relational: it arises through the ongoing fit between a way of living and the surroundings in which that life unfolds.

What Can We Know About Another Animal’s World?

The idea that different animals inhabit very different perceptual worlds is intuitive and has become widely accessible through writing such as Ed Yong’s 2022 book An Immense World. Yong describes sensory capacities that reveal aspects of the physical world unavailable to humans, including forms of vision, hearing, touch, smell, and sensing that can seem profoundly strange from our own perspective. This is an important corrective to the tendency to treat human perception as a general model of perception. But the enactive point goes further than cataloguing what different species can detect.

Alex Gomez-Marin (2023) makes a related point in reflecting on Yong’s book. Learning what another species can detect does not by itself tell us how those capacities participate in the enactment of its life. Scientific description can identify a stimulus, receptor, neural pathway, behavioral response, and evolutionary history, and each of those can answer an important question. A further question remains about how we should understand what the interaction is for the animal itself. Uexküll’s challenge was to keep that question visible rather than allowing the observer’s description of the parts and processes to exhaust the animal’s world of significance.

Similar caution is warranted when we move from perceptual capacities to subjective experience. Lacalli (2022), for example, uses differences in vertebrate brain organization to question how readily we should project familiar human forms of experience onto other animals. An animal does not ordinarily encounter its Umwelt as an Umwelt, as though it could step outside its own relations with the world and inspect them (Feiten, 2020). Humans can reflect on the limits of our perceptual world, and science can reveal features of the wider world that we cannot directly perceive, but we do not thereby acquire a view from outside every condition of embodiment.

Living systems and their surroundings undergo histories of recurrent interaction in which each provides conditions for changes in the other, without the environment simply specifying what the living system will do. Those surroundings include other living things, whose activities may themselves alter what becomes possible or significant. We collide with the world, but the world also collides with us, and it’s not so much a collision as an intertwining. Over time, bodies, activities, and environments change together. The world enacted by a living thing is therefore neither an inner representation of an independently specified environment nor a world freely constructed from within, but the meaningful field of relations that takes shape through an embodied way of living in a world shared with other forms of life.

References

Uexküll, J. von. (2010). A foray into the worlds of animals and humans, with a theory of meaning (J. D. O’Neil, Trans.). University of Minnesota Press. (Original works published 1934 and 1940.)

Brentari, C. (2015). Jakob von Uexküll: The discovery of the Umwelt between biosemiotics and theoretical biology. Springer. https://doi.org/10.1007/978-94-017-9688-0

Feiten, T. E. (2020). Mind after Uexküll: A foray into the worlds of ecological psychologists and enactivists. Frontiers in Psychology, 11, 480. https://doi.org/10.3389/fpsyg.2020.00480

Gomez-Marin, A. (2023). Six impossible worlds before breakfast. Current Biology, 33(10), R386–R389. https://doi.org/10.1016/j.cub.2023.03.070

Lacalli, T. (2022). An evolutionary perspective on chordate brain organization and function: Insights from amphioxus, and the problem of sentience. Philosophical Transactions of the Royal Society B: Biological Sciences, 377(1844), 20200520. https://doi.org/10.1098/rstb.2020.0520

Maturana, H. R., & Varela, F. J. (1980). Autopoiesis and cognition: The realization of the living. D. Reidel.

Thompson, E. (2007). Mind in life: Biology, phenomenology, and the sciences of mind. Harvard University Press.

Yong, E. (2022). An immense world: How animal senses reveal the hidden realms around us. Random House.