For a discipline so old, architecture is surprisingly self-questioning about its own nature. Much ink has been spilled to defend specific views on its aims and processes. Often, these views result in open discussions on the very fundamentals of the discipline. In contemporary debate, for instance, many authors discuss the role of interactions in architectural design. However, there is little agreement on the subject. Some authors consider architecture an object-centered practice; others, a relational one. In the first case, architecture is about the objects it builds. In this perspective, buildings are considered autonomous entities; architectural interactions directly depend on their formal, technical, and aesthetic qualities. In the second case, architecture is understood to be about its interactions. In this view, design processes depend on complex relations between heterogeneous agents, architects among them. These relations also influence the possible success of an intervention.
In recent years, architectural interactions have become the center of many important reflections. However, they are not addressed with sufficient clarity. Many authors discuss them as if they were equivalent or comparable. But they are not. Interactions between buildings and human agents, for example, are different from those with nonhumans. Nor are the interactions that a building establishes with people who work on its construction, and who live in it, the same.
Recently, an interesting debate between actor-network theory (ANT) and object-oriented ontology (OOO) focused precisely on the role of interactions in design processes. The main point of disagreement between these positions is the degree of autonomy of buildings. According to ANT, the identity of buildings is largely shaped by the interactions between various human and nonhuman agents. The former includes architects, clients, contractors, communities, and all the people directly or indirectly involved in the construction of a building. The latter includes the physical, climatic, economic, and sociocultural conditions of a specific context. The interactions between these agents play a key role in the design of a building, its construction, and its lifetime.
The role of autonomous and relational qualities is a major point of contention between both views. Autonomous qualities of a building, such as aesthetical and formal qualities, describe how it is per se, more than how it interacts with a context. Relational qualities describe instead how a building relates to its spatio-temporal surroundings. OOO defends the centrality of the former, while ANT—though never using the expression “relational qualities”—defends the centrality of the latter. In one case, the quality of an intervention resides mostly in its intrinsic, inner qualities; in the other, in the quality of its relations.
Figure 2. HH, human–human interactions (mediated by buildings).
Not all actors play an equally important part; but architectural processes are indeed relational 
. However, buildings are not the unprocessed result of existing conditions. Circumstances strongly drive the project at virtually every stage, facilitating some outcomes and complicating others. Even so, an intervention can sometimes achieve a result that, in its place and time, would seem unlikely. Architecture can defy circumstances. In some cases, it can even change them, by opening up previously unsuspected possibilities. This is the case with many monuments built throughout history. The Eiffel Tower in Paris, for example, at the time of its construction was unusually tall, relied on an unusual technique, and adopted an unusual architectural language, which was initially quite unpopular 
. Nevertheless, it was built and played a pivotal role in changing the public perception of iron buildings. By doing so, it paved the way for much later architecture.
HH interactions concern not only people involved in the design and construction of a building but also those who inhabit it. There are several ways to inhabit a building: by living or working in it or by using it occasionally. As humans, we are a highly interior species; according to Klepeis et al. 
, we spend almost 90% of our time in interior spaces. Most of our life is mediated by buildings, as are most of our interactions with other humans. Social interactions and daily rituals, when occurring inside buildings, are, in fact, a part of them. There is a connection between the architecture of a space and the events that occur in it 
. HH interactions change human agents, by creating social bonds. But they also change buildings, by affecting the way they are used and collectively perceived. It is also through HH interactions that buildings end up acquiring value for a community, which will ultimately decide how to use them and whether to preserve them over time. People are not an external addiction to a building; they are an integral part. Buildings are usually designed with the human factor in mind, considering how people could move, interact, use spaces, and react to their qualities. People play a fundamental role in shaping the identity of a building, based on how they live in it. It may be interesting, in this sense, to recall the case of the Torre David in Caracas, which recently has been the subject of numerous investigations. In 1994, due to an economic crisis, the financial center Confinanzas Tower—later known as Torre David—remained unfinished and unused. Some years later, a community of homeless people occupied it and gradually modified its spaces to adapt it to a residential function 
. However, the most important transformation of the building was probably not in its physical structure but in how it was collectively perceived. For some critics, such as Hancox 
, it went from being an incomplete symbol of modernity to an unpleasant vertical slum; for others, such as McGuirk 
, it went from being a symbol of financial power to a remarkable example of participatory architecture. In both cases, through human interactions, the building experienced a meaningful change.
3.2. Buildings–Human Agents (BH)
HH interactions describe how human interactions influence buildings. BH interactions describe instead how buildings affect the lives of communities and individuals (Figure 3
); they primarily concern the people who directly or indirectly inhabit a building.“Inhabit directly” refer to people who live or work inside a building or use it occasionally. “Inhabit indirectly” refer instead to those who may never enter a building but have a very close relationship with it. This could be the case of people seeing a building every day on their way to work, or from the windows of their houses, and so on. Habit, and the logic of affection, mediate our interactions with the built territory 
: we inhabit not only our houses but all the places and buildings that are part of our daily experience of the world. The relationship between buildings and human agents is neither neutral nor without consequences 
. Buildings change people. They do so by shaping everyday landscapes and giving a physical, visible presence to the place we call home. By doing so, they transform it from an abstract concept to something our bodies can relate to. At the same time, buildings also contribute to the construction of ordinary life 
: they facilitate certain kinds of actions, rituals, and events; they prevent others. Individual and social lives happen through architecture. This is also true at the city scale, where several studies have investigated how the built environment fosters gender inequalities and social segregation 
. There is a relationship between the dynamics of society and their places 
Figure 3. BH, building–human interactions.
Buildings can also interact with people who do not inhabit them, neither directly nor indirectly. They can do so by altering the social dynamics of a place: a street, a neighborhood, or even a city 
. People may not have a direct relationship with a building and yet see their life variously affected by it. Sometimes the construction of a building initiates a process of urban regeneration 
; in other cases, it can foster dynamics such as gentrification, by triggering processes that ultimately replace a community with a wealthier one 
. The radiating power of buildings—that is, their ability to directly impact the lives of individuals and communities—can extend beyond immediate surroundings. In some cases, it might also extend well beyond the moment of their construction. This is the case with monuments, whose influence can last for centuries, even millennia. Monuments change cities at two levels. They modify their physical, visible structure but also their very identity, by changing how citizens understand the history and legacy of an urban environment 
. Some buildings have such a strong radiating power as to inspire people who have never experienced them. One might have never been in the presence of a building, and only have seen it in a journal, book, or video, and yet be strongly influenced by it. When designing a project, architects usually turn to other buildings as references. Some of them may be buildings they actually experienced; most of them usually are not. Architects are constantly affected, both in their design and in their understanding of architecture, by buildings they only see in pictures.
3.3. Buildings–Nonhuman Agents (BN)
Cities and buildings are and have always been more-than-human territories, constantly modified, in their physicality and meaning, by several nonhumans 
). Some of these already have a place in architectural discourse; some do not. Nonhumans can be divided into three categories: nonhuman living beings (plants, nonhuman animals); nonhuman entities (objects); and nonhuman conditions, that is, conditions that, although related to human activities, still maintain an important degree of independence from them. Buildings, in this sense, are a specific kind of nonhuman entity. Nonhuman living beings may inhabit architectural spaces just like humans 
. Dogs, cats, birds, flowers, trees…many animals and plants may find shelter inside or in the proximity of buildings. In the Anthropocene, some of them are more likely to find a home inside buildings than outside 
. Every nonhuman maintains a certain type of relationship with the built territory. Pets have their own way of moving through it, depending on the species, size, and personality; plants do not move, but also relate to some characteristics of spaces, such as daylight and shadows; and so on. Buildings affect nonhumans; nonhumans affect buildings back, in their meaning and use. Analyzing the interactions between nonhumans and buildings could open the way to a rethink of architectural spaces, considering these other ways of living in them as well 
Figure 4. BN, building–nonhuman interactions.
Buildings also interact with elements of the urban environment and other buildings as well. The relevance of this interaction can hardly be downplayed; a significant part of the identity of neighborhoods and cities depends precisely on the way buildings interact with each other 
. Every building initially generates a state of tension with its surroundings, because it alters previous conditions and the visual–physical characteristics of a place. Such tension can be more or less intense and be perceived as positive, negative, or mostly neutral. This depends on many factors. One is whether the building confirms existing spatial qualities or proposes new ones. Another is whether the building is a loud object, distinct in scale and architectural intentions from the others, or whether it blends in 
Places are always defined by some material elements, such as buildings, and the immaterial but no less real network of interactions between them. Among nonhuman entities, interior objects occupy a special place. Objects can profoundly change the identity of an interior, by modifying its possible uses, atmosphere, or both 
. An empty room becomes a bedroom by placing a bed inside; or a study by placing a table with a chair, shelves, and some books. Traditional Japanese houses exploited this aspect of architecture. Most of their rooms used to be empty: they acquired a specific function only the moment someone placed some objects inside them—for example, a zabuton cushion and a low table 
During their lifetime, buildings can interact with various nonhuman conditions; a particularly important one is climate. Buildings are usually designed to suit the specific weather of a place. In addition, increasingly often buildings are intended to have as minimal impact as possible on the changing climate; it is the case of net-zero energy or carbon buildings 
. Weather conditions are also a factor determining how buildings age. A building erected in front of the sea is likely to age in a specific way, because of sunlight, salt, winds, and humidity; a building erected in the desert, or on a rainy mountaintop, will age differently. Daylight, which varies greatly according to season and location, also plays an important role in this sense. The amount of sunlight, its direction, and its intensity affect the way a building can be perceived, as well as its shadows and the brightness of its colors. The visual presence of buildings largely rests on their interaction with sunlight, whose changing conditions also affect their appearance over the day, the seasons, and the years.
3.4. Nonhuman Agents–Nonhuman Agents (NN)
Buildings are made by humans and, mostly, for humans. However, they are a theater of continuous interactions between nonhumans (Figure 5
). These interactions can be as heterogeneous as the actors involved 
. Pets can be harmful to plants. Furniture can be comfortable for pets. Daylight can affect the furniture. And so on. Plants have reduced mobility and stand in a specific place. Nonetheless, they interact with daylight and water. Indeed, this interaction is so important as to be vital. They may also interact with pets and, occasionally, with some ephemeral inhabitants of buildings, as bugs. Most importantly, plants interact with objects: the pot, the watering can, and, if they are small, the furniture they are on.
Figure 5. NN, nonhuman–nonhuman interactions (mediated by buildings).
Unlike plants, most pets can move freely around buildings; therefore, they relate to architectural spaces in ways that in many respects are similar to those of humans 
. They have favorite places; they use furniture for their comfort; they move around spaces according to the time of the day and the rituals to be performed. Pets with less mobility, such as turtles or fish, have a different relationship with buildings. However, they also relate to elements, such as daylight or water, and objects, such as the aquarium. Like humans, pets are directly affected, in their daily lives, by the opportunities and constraints presented by a building. A cat may enter a room only through a door or see outside only through a window; the placement of both doors and windows is a design decision.
Objects have an agency, and a very important one. The very idea of the agency of objects is one of the key points of ANT 
. Their agency is quite evident in relation to humans. Objects can enable activities that would be much more complicated, or impossible, without them. Without windows, it would be more difficult to regulate the amount of daylight and ventilation inside a house. Without doors, it would not be possible to open or close an interior as desired. Objects provide the paths for everyday life to occur. However, the agency of objects is also evident in relation to other nonhuman agents. A pot provides a plant a place to inhabit. A shelf may provide a place for the pot, so that the plant can have all the necessary daylight. A cushion gives the dog a place to sleep; a sofa, a place to rest. Objects also interact between themselves. The key interacts with the door, which will not open if the key is wrong or broken. A similar relationship exists between the handle and the door. A paper by Latour (1988) 
, for example, describes the complicated sociology behind the door-closer. But objects can interact between themselves in another, more subtle way. The identity of every interior partly depends on how its objects fit together 
. Each object has a presence and visual characteristics; these may or may not match those of other elements in a room. For interior architecture, the relational nature of objects is an important aspect. This is especially true in the design of spaces where objects are the real protagonists, such as museums 
. Architects such as Carlo Scarpa and Sverre Fehn emphasized how, in the design of their museums, they played a central role: for each object, the right placement had to be found, where it could maintain the most positive interaction with daylight, people, and other objects 
3.5. Building Autointeractions (BB)
Things, and among them, buildings, have an autorelational nature; they also maintain complex relationships with themselves, and these relationships are of great importance in shaping their identity. This is especially true for artworks or products of creativity, such as buildings. Each building presents various internal relationships: between materials and spaces, served and serving spaces, envelope and interiors, envelope and structure, structural and nonstructural elements, etc. (Figure 6
. Indeed, buildings may be designed from a particular internal relationship. In recent decades, several projects have investigated the interaction between the envelope and the interior spaces. In some cases, this resulted in the design of structurally and formally autonomous envelopes, in others in continuity with the interior 
. As such, buildings have a somewhat ambiguous nature. They have a unity, that is, they can be conceptualized as individual pieces. At the same time, this unity might be understood, to some degree, as a by-product of the interaction between their parts, elements, and subsystems 
Figure 6. BB, building autointeractions.
Usually, such internal relations go by the name of “form”. “Form” is a word that can mean different things; it might indicate the visual appearance of something, but also its internal logic, that is, the correspondences and interactions that structure something from within 
(Forty, 2004). The latter is the meaning scholars apply to the word “form” in this entry. According to Harman (2016) 
, this is also how the word is mostly used in contemporary architectural theory, even by approaches often seen as opposites. This is the case, for instance, of Eisenman’s insights on form 
and Schumacher’s parametric architecture 
On various occasions, Eisenman (1970, 1984) 
has argued for the intrinsic autonomy of architectural objects (Hays, 2009; Patin, 1993) 
. He intends “form” as the internal essence of architecture, the logical arrangement of its parts, as well as a means of comprehensibility. However, he also clearly states that form is indeed relational (Eisenman, 2006) (
, p. 89) and depends on the interactions between elements and subsystems of a building. Schumacher (
, p. 204), in his reflections on parametric architecture, focuses on function rather than form and on some occasions directly contests Eisenman’s position precisely for this reason. But his take on form is also relational: parametric architecture understands the architectural object as a field of parametrically defined interactions between its internal elements. In the contemporary debate, the idea that buildings are autorelational entities is widely accepted 
Even authors who consider buildings as autonomous entities, such as Eisenman and Schumacher, often understand their internal nature as relational, and see no contradiction in this. In fact, the autorelational nature of buildings not only does not contradict the idea of its autonomy but can be understood as the basis of such a claim. In its original meaning, the word “autonomy” identifies something regulated by internal, self-established rules 
. In this sense, buildings can be considered autonomous precisely because of the internal relations between elements and totality. Such interactions are different in every building, giving each one a unique presence and identity. The autonomy of buildings, in this sense, does not rest on their detachment from a sociocultural, physical context but on their formal congruence.
4. Buildings as Autonomous and Relational Entities
Architecture is usually considered either an object-centered practice or a relational one. As a consequence, buildings are considered either autonomous or relational: in their inner nature, in the process of design and construction, and in their interaction with a context. This is particularly evident in the debate between actor-network theory and object-oriented ontology. Theories such as OOO consider that buildings cannot be reduced to the sum of their interactions and focus on their autonomous qualities. Theories such as ANT consider that architecture is indeed about its relations and there is no possible autonomy for its objects. However, a closer look at architectural interactions reveals that autonomy and relationality are not opposing alternatives. They rather seem to be complementary aspects, which always coexist. If the word “autonomy” refers to something regulated by internal, self-established rules, buildings are autonomous because of the relational nature of form. Form is relational because it depends on, and takes its identity from, the interactions between parts, elements, and subsystems. If the word “autonomy” refers instead to something that has a certain degree of independence from its surroundings, buildings are autonomous because each one establishes peculiar and unique interactions with its context.
Conversely, the relationality of buildings depends, to some extent, on their objectual and autonomous qualities. The fact that a building is what it is—with its presence, materiality, and aesthetics—is an important reason why it maintains some specific interactions with the surrounding conditions, agents, and actors. How a building interacts depends on how it is per se; neither does its autonomous presence conflict with its relationality, nor vice versa. Autonomous qualities are relational, too. Aesthetic qualities, for instance, indeed determine how a building could relate to human and nonhuman agents in a given context. A beautiful, well-crafted building is likely to maintain different interactions than an unattractive one. Buildings are autonomous, because of their formal presence, and relational, because they create, and inhabit, various networks of interactions.