Introduction With the 21st century and its third industrial and technological revolution – characterized by the rise of microelectronics and computers- we are now in the age of “Hypermodernity”. Technology long ago has lost its status as simple tools. Throughout the history of the human race, technology always has played a distinct role in humanity's development. Don Ihde asks us to consider a very basic question concerning humanity's relationship with technology: “Could humans live without technologies?” [1]. His answer, based on empirical and historical fact, is simply no. Qualifying his conclusion, Ihde notes that “there are no known peoples, now or in historic or even prehistoric times, who have not possessed technologies in some minimal sense” [1]. Throughout human history, developments in techniques, manifested in both artifacts and processes, have accompanied developments in civilization. |
The characteristic of Hypermodernity is the high degree of interconnectedness. This is accompanied by loss of clarity and comprehensibility [2]. One side of this technological revolution is the mechanization of everyday world with the presence of information technologies. Our daily routine is not imaginable without computers. For many of us the Internet is more than essential and cellphones can be found in the pocket of everyone. But besides computers and information technology we are confronted with other machines which we want or must use: the automobile, the plane or the simple coffee machine in the office or domestic kitchen. All the technologies of our everyday world have one thing in common: We use them almost exclusively via the interaction with interfaces, or better called as “human-machine-interfaces”. But technologies with their interfaces is so deeply intermingled with our daily life, our “coping in the world” [3], that humans hardly or never draw their attention to it. We are aware of technology not until the occurrence of a “breakdown” [3]. The concept of “breakdown situation” in which technology is not working in proper order is defined as a situation of disappointed expectations. Technology is so ubiquitous, that it is the indispensable background for our life. But most of the time we are in the same situation as the fish, which is not aware of the surrounding water, his indispensable and habitual background. It can be no doubt that we live in a technologized world and that our interaction with technology takes place by means of interfaces. Therefore, in a not insignificant way, this interfaces shape our experience with technology and as well our experience through technology. |
This article is thus concerned with the often overlooked role of human-machine-interfaces. The aim is not just to provide an understanding in sense of a hermeneutics of technology, but also to ask the question: What has a philosophy of technology to offer, when it comes to the design and development of the human-machine-interface? In other words: Can designers or developers of interfaces derive concrete instructions and recommendations from philosophical Insights? |
To show that this is absolutely the case, I draw my attention to insights from the “phenomenological-hermeneutic” tradition, which is always concerned with the way reality is disclosed, interpreted and also experienced by human beings [4; 5]. Hence this work sees itself as a contribution to the liberation of philosophy from the ivory tower. The critical thoughts of philosophers should be applied on the stage of research and development, not only as a reaction to social and individual challenges of already established technologies and its effects [6]. |
Top Interface: Mediation Between Humans and Machines To avoid confusion we have to differentiate between the word “interface” and the term “human-machine-interface”. In a technical manner, “interface” is the point where two components of a technical system are linked. For example a plug-and-socket-connection for linking a device (printer, scanner…) to a computer. Put broadly: An interface is every surface that links two entities and shapes their common border. It is the region, where an interaction between two systems is made possible [7]. Likewise we can speak about interface as the contact-surface of a thing [8]. |
From this technical term of an interface we have to distinguish the “human-machine-interface”, which is the topic of this paper. This term denotes not the connection of two technical items but the place where humans get in touch with the machine, the very link between man and machine [9]. Main task of this special kind of interface is to close the gap between the user and the machine. Thus the challenge is the translation and coding of “information”, which have to be communicated between both of them, to achieve a smooth interaction [10]. The interface between a certain machine-and user, serves as kind of translator, which is mediating between two parties and makes one comprehensible to the other [11]. But the term “interface” must not be limited to machines. Our world is full of interfaces of various types, which we use to get in active contact with the things. Just think of the doorknob, which can be understood as interface between door and human. |
Another point is also mostly overlooked: We have to be careful not to think about interfaces as a one way street. We live in a world in which the interaction between men and machine is more than ever important to accomplish a task. Here interaction means the reciprocal influence of two units. Not just is the machine influenced by the user, but the user gets feedback and therefore is influenced by the machine as well! Machines and devices nowadays are equipped with a broad range of output mediums; hence it is absolutely insufficient to speak about human-machine-interfaces just in terms of input. Already the simple doorknob-example shows, that there is at least material feedback: the cold of the knob, the hardness, the stiffness etc. Phenomenologically speaking: There is never just input! |
More adequate therefore is an understanding of the user-interface that includes all discernible components of a machine which serve the communication- or better said: the interaction with the user. On the one hand these components can be operating elements, which help a person to handle a machine. Like levers and buttons. On the other hand, we find discernible reactions of the machine realised in the user-interface. For example messages on a screen [12]. We have to consider the user-interface as a double-track, with the activity of the user affecting the machine on one side. On the other side stands the machine, sending signals in user's direction to inform him about the results of his actions. The latter can be understood as feedback [13]. |
For a long time the everyday user of complex machines and computers is unable to understand the technical inner life of devices. At best he has a fragmented knowledge about the technical processes which take place in the boxes that occupy his everyday life world. This diagnosis is not very problematic, because the main concern of the user is the usefulness and proper application of the products. Apart from good quality and durability, secure and simple handling is very important factor. The interface makes it possible for users of high-complex apparatuses, which he does not understand, to fulfil his needs. If the interface allows a satisfying and successful use of the device and is appealing in terms of aesthetics, the potential buyer is more likely to buy this, rather than the one of a competing company, whose interface is not that satisfying. To a large extent the product appears in the interface [9]! For this reason the man-machine-interface is of great importance, because it can be crucial for the acceptance of a product. The advertisement for mobile phones seems to confirm this statement. Just take a look at i-Phone spots! |
They usually are advertised with special emphasis on simple management and innovative control elements. Because the problem of all interfaces is, that they are exactly what they are: Interfaces. They are in the way: An interface is always a form of barrier that stands between user and technical system [14]. The user therefore should be able concentrate his energy not on the handling of the interface, but on the task he wants to get done. Hence the design of the user-interface moves ever more into the centre of interest. |
Another important character of user-interfaces is, that they camouflage inner complexity. That interfaces really mask the complexity of a technical system can be observed by means of two examples: The computer, which can be found on nearly every desk and the thermostat of the central heating system. If the computer-user clicks a document on the screen with the mouse in order to move it, easily the impression can emerge, that he “really” moves the document. Instead he changed only a reference within the system. The “real” document consisting of zeros and ones is still in the same place on the hard drive [15]. One can go so far to say, the symbol (or icon) on the screen is an image of art. The spatiality on the screen is an illusion, since the data are scattered everywhere on the hard drive. They do not have a “physical home” in the real world [11]. |
Exactly in the same way the thermostat of the central heating system masks the basic mechanisms, which are responsible for the warmth. The machinery which is set in motion, if a small button at the temperature-regulator is turned, is entirely unclear to the user [16]. |
Closely related to this concealment of complexity is a further observation: There is a good reason, why complexity of the internal mechanisms of a machine is not made visible in an interface. Because the machine has to be usable! The interface has to ensure the appropriate use of the machine. In large part, the use is carried out through the interface. The success of this use depends on the conception, clarity and manageability of the interface. It is not so far off to say, that handling artifacts is actually handling the interfaces! Contrary to hitting a nail with a hammer, we rarely deal with a whole technical artifact. A successful handling of technology is therefore a successful handling of the interface. Thus a handling-knowledge refers to interfaces and not to technical systems overall. |
The last section revolved around the term “interface”. Furthermore, some important characteristics of the interface between humans and machine had been marked out. One of these problems is the concealment of complexity. Now I want to focus more deeply on what we usually call “human-machine-interface”. |
Top Two Sides of one Coin: Physical and Cognitive Interfaces When we talk about human-machine-interface or user-interface, we usually mean buttons, displays and switches. In short, we mean a certain material structure, which allows handling our everyday-devices: the physical interfaces. But this is just one aspect. If we want to think adequate about interfaces, our view needs to be complemented by another aspect: The cognitive side of an interface. But first some explanations about the “materiality” of human-machine-interfaces: |
The physical interface The term “physical interface” covers the physical in- and output devices, which put humans into the position to interact with a machine [17]. Physical input devices are for example the computer mouse or the keyboard. But also simple knobs at the radio are physical interfaces, since they are a physical structure which is placed between users and their technology. But there are also interfaces which are simultaneously used as input-device and to convey information. A touch-sensitive screen, also called Touchscreen, is a technical artifact, in which this bilateral relationship is materialized. The user receives visible information via the screen and at the same time acts through this screen by touching him lightly. When we take a closer look at it, there emerges a common characteristic for all physical interfaces: The interaction between device and user is always closely connected to the physical structure of the interface. This physical structure in turn, has a close relationship to the human body. In order to be able to handle a computer mouse, I need a hand. Exactly the same with the steering wheel of a car. And in order to be able to recognize information on a screen, I must possess sufficient eyesight. One could go so far to say, that the information transfer through interfaces forces humans to encounter their own body [18]. Handling physical interfaces aims on special competencies in handling one's own body. These skills are always more or less successfully taken into account in the development-process and design of interfaces. In the design of an interface we can find the designer's expectation towards the user. The interface is therefore always a kind of connection between the user and the designer of a technical artifact. By means of this competencies or skills with regard to handling interfaces comes something into play, which is a topic within the phenomenological tradition since Edmund Husserl: The lived and experienced body (German: Leib)! As humans we are not only passive physical bodies in a physical world, but exhibit a body which makes experiences, is animate and actively merged into the world. Also it is a body shaped by culture. From a phenomenological point of view it needs to be emphasized, that the relation between human and machine is bilateral. We do not only use machines, but they also use and change us in a certain kind of way. Our body adapts to different types of technology and technical contexts. But technology must adapt to humans as well [6]. A technology which does not fit our body (both physical and lived body) is difficult to use, disappointing and sometimes disturbing. Our body is our connection to the world. We move and act in this world by means of our body. We deal with the things in the world and give them meaning using our body in an active way. These things in the world demand our attention on very different levels. We are not only challenged in a cognitive way, but also physically, since in the interaction with these things our body is indispensable. That is true for handling simple tools like a shovel, which demands certain body movements. But it is also true for the use of a keyboard, whereby different physical actions are needed. There are for sure huge differences between digging a hole and typing a letter on the keyboard, but both make use of implicit competencies, which are embedded in the human body. Both types of human practice are possible only because humans possess certain sensorimotor skills, which allow using the body in the right way [19]. From the numerous insights of phenomenology regarding the human body, we can draw valuable advices for the design of physical human-machines-interfaces. At the same time these insights also throw a light on the question, why handling some interfaces is more easily than handling others. Whether we find a thing attractive or not, is an unconscious reaction to the surface structures of this object. But not only attractiveness is connected to the visible surface of an object. Also the handling with such an object is linked to its visible parts. Especially technical artifacts such as machines should offer visible clues for their use. Therefore one of the most important design-principles should be the visibility [20]. Visibility means, that the important parts of the device are conceivable and convey a message, how to use it. With regard to phenomenology, many things in our environment are simply not “only there”, but they want to say us something. They are stimulative; they request something [21]. Many things request a certain way of handling. An everyday non-machine example is the knob at a door, which requests pulling. The mentioned “request-character” of things is in close relationship to our body and our acting in the world through the body. Our experience of the world is in a very deep sense linked to the way in which we act in it. Our experiences cannot be separated from our bodily presence in the world [22]. The knob at the door provokes pulling, because its visible form provokes exactly this and no other sensorimotor skill. The request-character is closely connected to the perceivable characteristics of a certain thing. These perceivable characteristics tell us, how to use a thing. This phenomenological insight is of value for an investigation of the man-machine interface: Since correct handling of a machine depends on the interface, the interface should guide this handling. The physical interface should be arranged in a way that requests or prompts the appropriate use. A control device at a machine, which has the form of a lever, demands pulling and not turning. Likewise a button requests pushing. The design of the physical human-machine-interface should embrace the request-character of things in order to ensure an appropriate, satisfying and safe use of the machine. Closely related to the request-character of machines is what can be called “sedimentation”. This term refers to the habitual interactions with a device. Or in other words: The “force of habit” [23]. The relation of the person to a certain device is sedimented if this person is strongly inclined to experience and use this device in a particular kind of way. For example regular computer users are inclined to interact with the mouse in a special kind of way. The topic of sedimentation seems to be very important in the field of the innovation or improvement of interfaces: The break with the habitual interactions can be very unsatisfying and even dangerous for the user. What is said about sedimentation also applies for the cognitive interface, which is the topic of the next paragraph. This short example has shown that philosophy, in the shape of phenomenology, can make an active contribution to the development of user interfaces. Therefore the reading of phenomenological texts can only be recommended to design-teams. Physical interfaces, such as buttons and switches, are an important element of machines of various kinds, but they constitute only one half of what is called interface. Especially with the rise of digital information technology, another type became ever more urgent: The cognitive interface A basic feature of modern technology seems to be, that either the interfaces are difficult to handle, because they have to combine a huge amount of functions, or they are arranged in a simple way and are thus easy to handle. The consequence of the latter however, is a loss of flexibility, since many functions are not available anymore. Mostly we concentrate on things when they do not function in a proper way or when they are difficult to handle. Usually things fade into the background of our awareness while we handle them. At this point I can refer to Martin Heidegger: “What everyday association is initially busy with is not tools themselves, but the work” [24]. We are only aware of things as things, when there is a “breakdown” in our experience of technology. A breakdown can have a material cause, like a stucking key on the keyboard. But this is not the only way a breakdown can occur. There can be a breakdown, despite the smooth technical functioning of the interface. Because whether we regard an interface as effective or not, is also a question of cognition. Like in everyday-life actions, cognitive processes play a huge role in handling a machine. Information needs to be processed, attention is requested, memory is stressed, problem solutions must be found and much more [7]. How information is picked up for example is influenced by composition of the surface. If the surface is visually overloaded, more cognitive capacities must be spent in order to filter the substantial information for the task at hand. A breakdown can thus have technical or material, as well as cognitive causes. For this reason, the cognitive interface must be arranged as carefully as the physical interface. But what do I mean, when I talk about a cognitive interface? Roughly speaking a cognitive interface is understood in the following way: The user always interprets the system-performance while handling a machine. Furthermore, what the user has in mind is a model of the task, and the goals which he want to achieve. Task of the cognitive interface is, to bring the interpretation of the system performance and the model of the task and goals in line. In other words: The system performance, which shows up in the interface, must be in harmony with the users’ model of the task. Moreover, the user must be able to fulfill his desires and intentions [10]. The user needs a mental model of the machine, in order to handle it effectively. He needs an understanding of the activities that need to be done for accomplishing certain tasks. The users’ model also contains a knowledge, which allows him to foresee the system-performance, if a certain command is given. This model must be arranged and affected by the interface. The designer must implement an explicit conceptual model that is easy to understand and learn, if he wants the user to understand the system [17]. What needs also to be ensured by a clear model is the reliable predictableness of system performance. Predictableness is an important factor for habituation and confidence, which in turn both are very important features for the handling of technology. To illuminate what's being said, I will now turn the attention to a familiar device: The personal computer. With increasing digitalization of devices and machines, one can't see their abilities and features at a first glance. Nowadays, form and figure of equipment reveals very little about what they actually can do and what their functions are. With regard to design only, one can hardly distinguish between devices [25]. Today it is possible, to have many applications blended in one device. An outstanding example of this is the computer. All actions of the user are by means of physical interfaces pressed into a homogeneous structure [26]. With a standard computer, one can find three physical interfaces: screen, mouse (or Touchpad) and the keyboard. These interfaces only allow a limited repertoire of actions. One can click the mouse, write with the keyboard and stare at the screen. Despite this limited number of physical interfaces and the limited possibilities of (physical) interaction that come along with them, an immense number of activities and tasks can be accomplished: editing pictures, playing games, surfing the web and so on. Only to write letters is almost archaic. The mass of activities made possible by a computer is not the outcome of a multiplicity of physical interfaces, but the merit of digital programs and applications. Since all of these programs make use of the same three physical interfaces (which don't change their shape), their satisfying use depends on the conceptual models, which are presented by the programs. Therefore the world of software programs is not so much a world of physical control over a thing, but rather a world of cognition. In this world ideas and concepts present themselves without physical substance [27]. Since the physical interfaces stay the same, they don't give a clue for the correct handling of computer programmes. Clicking the mouse and writing on the keyboard are utilized by all programs. What is of importance for the handling of these programs is the conceptual model that they provide to the user. What is presented on the screen must be clear and transparent. The different symbols and user-surfaces should explain themselves. Or at least they should make clear enough, which option lurks behind which symbol. If the conceptual model is understandably and easy to recognize, then handling the program will be satisfying. This conceptual model is to be understood as cognitive interface, since it shapes the interaction between user and device just like the physical user interface shapes it. By example of the computer I have shown that few physical interfaces (mouse, keyboard and screen) can coincide with a multiplicity of cognitive interfaces (mental models of the programs). The limited quantity of physical interfaces, with a simultaneous multiplicity of cognitive interfaces raises own kinds of design-problems. Developers have to be careful that the conceptual model which they want to present, is compatible with the physical interfaces. A good conceptual model is a fundamental condition for the successful handling of equipment. The user needs a good concept about what is going on. He needs an understanding of the different options and alternatives of action, as well as of their influences on the device. The cognitive interface must present an easily graspable and understandable conceptual model of the system-behavior. This model should be graspable and learnable with a minimum of effort [26]. Furthermore the model must integrate the different actions of the user into a coherent whole. It must evoke the feeling that he is in control and not the device. Good cognitive interfaces should not reflect the innovations of technical development by trying to integrate all what is technically possible. Instead they should adapt to the habits, perception and thinking of human beings. Moreover they should take into consideration the aforementioned habitual interactions or “sedimentation”. But there is also a need for them to adapt to the environment of use. This is striking if we compare the classical desktop computer and mobile infotmation technologies such as cellphones or PDA's. The environment of use for the desktop computer is totally different than that of the mobile information technologies. The first require sitting in front of a desk in a more or less comfortable chair, whereas the latter are involved and engaged in the world [28]. Thus different cognitive services are needed. During the use of mobile technology attention has to be shared between the device and the surrounding world. Therefore visual output should be complemented by other channels such as audio or force. Due to the different environments of use, the development of interfaces for mobile information technology should not rely on the “desktop-computing-paradigm”, which assumes a legless and worldless user [26]. The next step is to focus more explicit on philosophy of technology contribution to interface design. Top Embodied Mind: Phenomenological Investigation of Human Machine Interface The “desktop”-metaphor for the interaction between user and computer reflects what with respect to Heidegger can be called “being-in-the-world” or embeddedness. For Heidegger it is clear that the most important way how we encounter the world, is the practical coping with it [29]. Implied is the insight, that the individual cannot be separated from the world in which it lives and acts. Embeddedness does not mean simply physical manifestation. It means to be rooted in and emerging from an everyday experience of the world. Our acting and coping in and with the world is fundamental for our understanding of it. We give sense to the world regarding the way we cope and act in it. An embedded action is always the creation of meaning by coping with artifacts and things. Embeddednes is best understood as a characteristic of our engagement with the world, which makes this world meaningful for us. In short: Embeddedness is the relationship between action and meaning [22]. |
The conceptual model “Desktop”, which functions as cognitive interface within the human-computer-interaction, reflects exactly this embeddedness of humans into their everyday context. The desk has already a fixed meaning for many computer users. It has this meaning due to practical handling with it. On the desk one can find documents, papers, files and so on. One is coping with these things in practical ways: Papers are shifted from one side to the other, thrown into the waste-basket or filed in records. The implemented ´“Desktop”-model on the computer screen makes use of these meanings. Here as well we find documents which can be shifted, deleted or put in an archive. Without problems the user adapts to this concept, because it corresponds with his practical experiences, with his bodily embedding in a meaningful world. The cognitive interface fulfils its purpose, because user-model and system-model are in line. |
A direct lesson for the design of cognitive interfaces can be derived from this example. The conceptual models, which are at the bottom of cognitive interfaces, should be aligned to the embeddednes of human beings, in order to make a successful handling of a machine possible. Designers and developers should orient oneself to the implicit knowledge, which users already possess through their coping with this world. By their coping with different situations, things and language humans acquire certain cognitive patterns and implicit knowledge [19]. Cognitive interfaces should take this bodily embedded knowledge into account, instead of imposing new and difficult user-models upon users. In order for the cognitive-interfaces to really make sense, they have to fit to the structures of experience, to the “being-in-the-world” of humans. |
The connection, or better the interrelation, between physical and cognitive interfaces is open to philosophical inquiry and descriptions. From these descriptions one can derive fruitful advices for the organization and design of this interplay. |
Let's take the computer-mouse, a physical interface, as example here. As cognitive interface I assume a normal user-surface on the screen; including the white mouse-arrow, which indicates the place on the screen, where different actions are possible. While being engaged with these interfaces, it doesn't take long until the awareness is not on the hand movement anymore, by which the mouse is moved. The bodily relation to the mouse fades into the background. The motion of the mouse is less apparent to the user, when engaged in a work in front of a screen [23]. Instead the attention is directed entirely to the events on the screen. Is there something to be clicked on, e.g. a document, the users’ awareness is not explicitly on the mouse. Instead: Seeing the document, the wish to click it and the movement of the hand are blending. The mouse is now a part of the (lived) body and the body thereby extended. The user refers to the different objects presented on screen through using the mouse. The artifact, here the mouse, is incorporated into the bodily experience [30]. This observation corresponds with the considerations of the great French phenomenologist Maurice Merleau-Ponty. For him perception is not thinkable without action. Any perception presupposes action. Merleau-Ponty understands the body as a priori means, by which we are intentional directed to the world [31]. What applies for perception is also valid for consciousness says Merleau-Ponty. Consciousness is not “I think”, but primarily “I can”. The body has the ability to orient itself in the world, to acquire habits: “Consciousness is being with the thing by means of the body” [32, my translation]. In his relationship to the thing, the body acquires meaning. These meanings are a knowledge, which comes from the intimacy in coping with things in the world. There is a knowledge “that is in the hands” [32, my translation]. The body is not driven by an intentional consciousness, which exists independently of it. Instead, intentionality belongs to the body itself. This physical intentionality is the fundamental connection between humans and their world [33]. |
The mouse as physical interface meets this bodily intentionality. The mouse is small and not disturbing, therefore can easily be incorporated into the own body. The body is extended by the mouse in such a way, that the user acts through it, with his awareness on the screen. The movement of the mouse goes on unconsciously; one would like to say automatically. In handling the mouse, it seems that the document on the screen is in a direct range. One has the feeling of an active coping with the document, the feeling of direct manipulation. This is positive, because the user is accustomed to the direct manipulation of all kind of objects from his everyday life-world. The computer-mouse as physical interface makes use of the users embodied skills and habits. But it should be clear by now that the physical interface is only one half of the story. In order to ensure a good interaction between human and his computer, it is not sufficient if only the physical interface put the bodily skills to account. The cognitive interface must support the handling made possible by the physical interface. To remain in our example: The user-surface in front of the users’ eye must allow the user to fully appreciate the “knowledge that is in his hands”. The underlying model of the cognitive interface must present the information in such a way, that a bodily orientation is easy. The ability for direct manipulation used by the mouse as physical interface is worthless, if there is no support for this ability on the cognitive level. What is presented on the screen must be easily recognizable for the user. It has to correspond to his expectations. If he does not understand what is going on the screen and what he has to expect, direct manipulation is worth little. The extension of the body cannot counterbalance cognitive understanding. And vice versa: The best cognitive interface, the most innovative and interactive user-surface, does not enhance the handling of a machine, if it does not consider which possibilities are realizable on the level of the physical interface. |
Thus, a good handling of the machine (in our example the computer) is only possible, if the interplay between physical and cognitive interface is harmonious. We have to think about mind and its competencies as bodily embedded [19]. With this in mind, the Cartesian dualism of body and soul, mind and matter, is totally unfounded. There is no dualism; they are not separate, but connected. This interplay should be considered by developers. Only then the outcome of the design-process can really be satisfying. Designers and developers should keep this in mind, when it comes to the development of so called “user-friendly machines”. They should think of physical and cognitive interfaces as connected and interrelated. An intuitive and easy handling is only possible if this thought flows into the construction procedure and the interface design. |
Top Conclusion This short paper about physical and cognitive interfaces showed, that an interface is more than the superficial material structure of a machine. We have to rethink about interfaces not only in terms of buttons, screen or computer-mouse, but also in terms of a mental or conceptual model, which is presented to the user through these interfaces. |
Notably with digitalization and the triumphal procession of the computer, cognitive interfaces gained more and more importance, since now many applications are possible with one device. This variety in application and the restriction on few physical interfaces (mouse, screen, and keyboard) require handling-models, which can easily be understood by the user. Thereby cognitive and physical interfaces must be thought as a unit. They are as a team responsible for a successful handling. |
In the inquiry on interfaces I dealt with philosophical considerations. In doing so I hope to have shown that they are valuable not only for a theoretical understanding and an interpretation of interfaces, but likewise for the design process itself. It is now up to developers of technology to hear the voice of philosophy. |
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