For centuries, the prevailing image of the human mind has been that of a sovereign entity residing securely within the physical boundaries of the skull. Our culture, language, and science have reinforced this view, portraying the brain as a biological computer, a cordoned-off space where the exclusive work of cognition happens. This perspective appears increasingly incomplete. The mind resembles a nest-building bird, constantly plucking materials from its surroundings—a twig here, a bit of string there—to construct a functional whole. For humans, these materials are not just twigs and string, but the feelings and movements of our bodies, the physical spaces we inhabit, and the other minds with which we interact.
This process of "coupling" with the environment is not a new phenomenon. We have been extending our cognitive capacities into the world for millennia, from the earliest cave paintings that served as external memory stores to the intricate knot-based records of the Inca. We are, and have always been, inherently extended beings, fluently integrating external resources into our most intimate mental operations. In Gods and the Porous Self, we described the "porous self" of antiquity—a mode of being where the boundary between the human mind and the world was permeable. For our ancestors, the environment was not a collection of inert objects, but a community of active forces. The river was more than water; it was an agent one negotiated with. The world acted back.
Modernity brought the "buffered self," sealing the mind within the skull and reducing the world to "dead matter"—silent, predictable, and indifferent. This disenchantment granted us autonomy and scientific control, but it came at the cost of isolation. The current technological epoch has funneled this impulse into a specific, and limiting, channel: the glowing screen. Our smartphones and computers are undeniably powerful, but they are "portals" to a disembodied cyberspace. They demand we leave our physical context to engage with them.
This chapter argues that we are undergoing a shift toward agentic materiality. Through the integration of responsive systems into our architecture and artifacts, the environment is regaining the capacity to sense, react, and interact. Rather than a regression to the superstition of the past, this represents a progression toward a "coupled" future where our environment becomes a sophisticated partner in our cognition. The goal is not the utilitarian "automated home" that optimizes convenience; rather, it is a "resonant hall" that scaffolds our rituals, enforces our norms, and extends our capacity for meaning.
Before we can construct a new kind of architecture, we must first reconsider the nature of the mind itself. The conceptual groundwork for an architecture that participates in cognition was laid not in a design studio, but in a 1998 philosophy paper by Andy Clark and David Chalmers titled "The Extended Mind". Their argument, at once simple and radical, proposed that cognitive processes "ain't all in the head". This idea, known as the Extended Mind Thesis (EMT), provides a powerful lens for re-examining the relationship between ourselves and our surroundings.
The core of their thesis is "active externalism". Unlike passive external features (like a book sitting on a shelf), active externalism posits that in certain situations, the environment plays an active, real-time role in driving cognitive processes. The external features are coupled with the human organism in an active feedback loop. When this coupling occurs, the external components play an ineliminable causal role. The classic example is the act of playing Scrabble. A player who physically rearranges the letter tiles on their rack is not merely performing an action to aid a subsequent mental calculation. The physical rearrangement of the tiles is part of the thought process of discovering a word. The world, in this case, functions as a process that, were it done in the head, we would unhesitatingly recognize as cognitive.
To make their argument more concrete, Clark and Chalmers introduced the thought experiment of Inga and Otto. Inga hears about an exhibition, recalls the address from her biological memory, and goes. Otto, who has Alzheimer's, relies on a notebook. He looks up the address and goes. Clark and Chalmers argue that Otto's notebook plays the exact same functional role for him that biological memory plays for Inga. The information is reliably there, easily accessible, and automatically trusted. To say that Inga's memory is part of her mind but Otto's notebook is not is to betray a prejudice for what is inside the skin. Functionally, Otto's mind has been extended to include the notebook.
The thought experiment begins with a portable artifact—a notebook. But the principle invites a radical expansion of scale. If a notebook can be part of the mind, what about the buildings we inhabit? The built environment is arguably the most constant, reliable, and complex cognitive artifact we create. It is the scaffold upon which much of our mental life is built.
This suggests a powerful contrast between two types of environments. A sterile, minimalist environment offers little for the mind to couple with, forcing cognition to retreat back inside the skull. A "coherently complex environment," however, provides a rich substrate of information and structure, allowing the mind to extend outward and enter into a reciprocal interplay with its surroundings. The objective of agentic materiality is to transform our environment from a passive container into an active cognitive ecosystem—a habitat where the environment and the individual co-create thought, action, and experience.
The philosophical argument for an extended mind finds compelling support in the fields of cognitive science and neuroscience. Before the mind extends into notebooks or buildings, it extends throughout the body. The body is our primary interface with the world, and it is through our physical engagement with our surroundings that cognition unfolds.
Embodied cognition posits that our cognitive processes are deeply rooted in the body's interactions with the world [1]. Thinking is not confined to the brain but is shaped by our entire physical form—our sensory organs, our limbs, our posture, and our movements. Research shows that radiologists are faster and more accurate when they can walk while studying images, and children solve problems better when allowed to gesture. Our very language is built on bodily metaphors, such as "grasping an idea."
The enactive approach takes this a step further, describing cognition as a "loopy" and dynamic process that emerges from the continuous, reciprocal interaction of the brain, body, and world. From this viewpoint, we actively enact a world through our sensorimotor engagement. Consequently, architecture is not something we merely perceive from a distance. It is a domain of potential action that we bring into being through our movement. We think with and through our built environments.