Crossing borders and removing borders currently dominate cultural and scientific debate to an ever greater degree . The human body stands as a particular focus of interest in all this. The traditional marking of borders, such as that between man and machine, materiality and immateriality, reality and virtuality seem to shift or even to dissolve completely. This is welcomed on the one hand, as the hope has been articulated that in this way hierarchical structures which were associated with the inherited dichotomisations can be broken down. On the other hand the removal of borders also arouses fears, because current trends seem to be dominated by techno-rational attitudes and economic calculations.
At present various reactions to this may be observed: Thus, referring to the body there is one plea after another for the recognition of an own dynamic of the physical, of a robustness of the inner as well as outer nature and of the significance of a dimension which in the end is indeterminable and beyond language. At the same time, various different critics are trying to investigate the ways in which the paradigms of computer science dominate discourse about nature, materiality and physicality, and how, in a subtle fashion, a form of jargon is creeping into the language, which tries to define mechanical and organic processes using the same terminology. Physical and cognitive processes are currently being described with metaphors taken from computer science in just the same way as mechanical and artificial processes in artefacts. The traditional differentiation between the natural and the artificial, and the gap between material and immaterial phenomena is increasingly called into question, and accompanied by thoughts on new definitions or final overcoming of these distinctions. This is particularly true in looking at concepts of body and identity.
A shifting of borders of this kind can at first be perceived as a stimulating challenge, to subject traditional dichotomies to a renewed critical reflection and examination. However, in some areas it would appear that these new definitions are characterised by an attempt to found a new "universal science", which cuts out the particular, beyond the accepted point of view in favour of a theoretical approach, which negates all differences and endeavours to overcome any form of marking borders.
In the following text it is my intention to explore the way in which a look at the experienced body calls the traditional borders, accepted since time immemorial, into question, and how the shifting of borders which may currently be observed can also be used to redefine the "self" in a way which has long been possible (and has sometimes also been articulated). In doing so I shall interpret the experienced body as an existence which has always embodied both the absence and presence of borders shaping the way how people are getting in contact with each other and how they are embedded physically in the material world. As well, I would like to underline the necessity of considering the particular characteristics of material bodies to reject visions of an immaterial self as well as demonstrating the limits of virtual contacts.
If physical borders and the crossing of these borders are not only to be defined in the metaphorical sense in their significance for the outlining of the self, then a look at the skin as a somatic-material border to the material body offers us a place to start examining the matter. A reference to the tactile dimension follows naturally from this, as feeling, or the sense of touch, guarantees that continuous contact with the world, through which the individual shapes his own outline. Touch, as a significant form of access to the world, however, always implies a duality of meaning, which is characteristic of the experienced body in general: a duality of the self, according to which, as the touching existence, one is not only always simultaneously the subject and the object, but also which shows a continual crossing over regarding the self and the other.
So the phenomenon of touch draws our attention to the fact that physicality is always responsive physicality, i.e. that the border between the self and the other which has hitherto seemed clear, is a modern construction, which can only be upheld by cutting out the physical constitution. A look at the actual experienced body  therefore refers us to an interdependence of the experienced body and the world, to an on-going process of dialogue, which has always made the demands of the modern subject for autonomy seem questionable, as this also occurs through the reference to its socio-cultural and linguistic embeddedness.
To conclude this essay, it will be shown how from the limit demarcations between the material body and the environment, nature and culture, man and machine, now perceived to be open and continuously changeable, a concept of the physical self can be derived, which is seen to be situated, hangeable, open and bordered at the same time. In doing so it will become clear that the removal of borders should not be thought of as total, but is always accompanied by self-constituting acts which themselves set borders and which differentiate between themselves and the others. The conception of a physical, "responsive self" shows that this is bordered and borderless at the same time.
II Visions of tactility and contact without and beyond borders
Cyberspace is regarded as a prototypical area with no borders: there is talk of the "global village" in contrast to the "city jungle"  , which metaphors suggest that virtual contacts in the borderless dataspace would allow us to experience again the intimacy of immediate contacts, which modern people have lost along the way in the process of civilisation. Numerous authors have also pointed out that the intercultural communication practised on the net can allow traditional barriers between different cultures and nations to be overcome. The limits of these visions have very well been documented by Charles Ess  and others. And furthermore, hybrid hermaphrodite beings, often called cyborgs, which "embody" an amalgamation of organic and technological processes and are seen as a new narrative strategy, carry the great hopes of post-human visions . 
If we are to believe Philip Queau , then in virtual space the bodily shape and body image, material body and discursive body-construct are blurred together: dichotomies, that is, which until now upheld a division which was fundamental to the constitution of the self. The skin borders of the situated experienced body seem to flow into a space which is no longer determinable, and the concrete opposite, which until now one rubbed up against in the literal as well as the metaphorical sense, remains incomprehensible in virtual contacts as an immaterial construct and is malleable according to individual fantasy.
Derrick de Kerkhove  is one of the theoreticians of cyberspace, who talks of a borderless tactility and develops visions, in which our physical borders dissolve in global cyberspace. He starts by assuming that every interface between person and computer is an adaptation of the ability to touch and be touched. In doing this he refers primarily to machines, which react to pressure, movement and touch, and thereby enable us to "find our way back to an elementary palpability". In this connection he speaks not only of a global proprioception, but also of an extension of the skin by means of electronic communication networks. He maintains that the new skin of the technologically transformed material body shows a universality without borders, which no longer binds the individual to a certain place and no longer makes his touch dependent on concrete contacts with other people. As an example he takes an installation created by the video artist Sermon, in which two people who are physically situated far apart from each other can make contact with each other via a screen monitor and a touch screen, and the touches of the two of them become a product of their own imagination. The installation artist Stelarc also illustrates with his technological removal of the borders of the skin, that new technologies lead to a new interpretation of the bodily exterior, so that the bodily shape might change and we might be able to break through the borders of the material body which have so far been familiar to us.
But what does universal tactility mean? When we are "moving" within the net, according to Kerkhove there is no longer any absolute border to the material body through the skin. What we are talking about here is most decidedly an extension of the borders of our skin in the sense of the formation of an "orbital exterior for planetary thinking", as in the world of electronic communication, the skin exterior of the traditional body is displaced into the global network. Moreover, in the debates about cyberspace there are visions and sketches of communication practices, which are only inadequately described by the concept of virtual sex, but which are characterised by comparable tendencies towards a de-materialisation of contacts. 
Kriesche  speaks in a similar fashion of a third body, that of the data dandy, which may be established somewhere between materiality and immateriality, between body and soul, between reality and data-world. It is a liquid body which can live on in the net beyond its physical vulnerability as a "dataface" or collection of data, which leads a life of its own beyond the realm of any materiality, which until now bound it too tightly to a here and now and subjected it to time and space borders. As an example of this Kriesche cites the Avatars, which are enjoying increasing popularity, which when coupled with "softbots" can lead a life of their own independent of their creators, and which represent a dematerialised crossing of the borders of the material body.
In similar fashion Moravec  dreams of transforming sluggish lumps of material into flexible computer elements: "Living beings will no longer be defined by their physical and geographical borders, they will develop, expand and defend their identities as transactions of information in cyberspace." And also in the increasingly widespread new interpretation of the material body as a collection of regular circulation systems, the code for which can be deciphered and applied to machines, we see a conviction which is increasingly prevalent: "There are no essential differences or absolute demarcations between bodily existence or computer simulations". 
In general it may be said that, despite the gloomy visions of doom which are equally to be found, the increasing borderlessness and de-materialisation of the self through electronic media and technologically advanced apparatus is frequently described as a form of liberation, which allow the individual to unfold and expand the "self" and develop new contacts beyond the borders set by the material body and by others.
III The Skin: Border and permeability of the body
The concepts of universal touch and a borderless exterior for the material body, developed in the context of "cyber-utopias", seem to suggest that we need to approach the particularity of human skin and the phenomenon of what is tactile again, from a different perspective: "To jump out of your skin"; "something gets under your skin"; "to only go skin-deep"; "to be thick- skinned/thin-skinned"; "to save your skin"; even colloquial language demonstrates the deep significance of the skin in its many and various functions. Often the skin is seen as the outer surface of the organic body as well as being the bordering surface between the material body and its environment. The skin also seems to provide a guarantee of the unity of the body and from this point of view it takes on the function of a self-constituting and self-securing protective exterior for the self. Thereby the skin is a border and an opening at the same time: on the one hand it offers protection from the influence of external irritants which could pose a potential threat to the organism, but on the other hand, through its permeability, it stands in constant contact with the world. Biographical and social experience are written into the skin as if onto a sheet of parchment, i.e. in wrinkles, scratches, scars and cuts we can see a materialised form of the cultural record of experienced bodily individuality.
At the latest since the work of Anzieu  the skin, or rather skin contact in early childhood has come to be seen as constitutive for the development of the self which is why in the context of onto-genetic research there is also talk of the "skin-self" or "peau-moi": according to a psycho-analytical interpretation, the first skin contact with a contact person who breast-feeds, strokes, embraces, supports and cuddles the new-born, is important for the development of the self in later life, as in the symbiotic relationship between the new-born and the carer the baby first feels safe and protected. The carer's skin and the baby's skin are still merging together, until the baby starts to look at something. In this moment, in which the baby perceives itself as a being which is different and separate from the carer, the process of individuation begins. So while in the first phase of life, the new-born is in constant contact with his/her carer via the skin, and so at the beginning lives in a state of symbiotic unity with this person, it is only with the new-born baby's glance, at first empty and then only gradually directed at things and people, that the process of distancing of the self and the other takes place and thereby a gradual constitution of the self. In the course of this process the skin, as a bordering and protective exterior, takes on "a function of individuation for the self, which transmits the feeling to the self that it is a single being" and to be distinguished as such from others. The first skin contact with the world can therefore be regarded as a stage of development, where the border between the self and others is not yet fixed but instead suggests more of an open continuum. In this way the skin not only enables the baby to make its first contacts with others, but it as well the period where the border between self and not-self is newly constituted, over and over again.
Thus, the skin can be perceived as the exterior of the material body, which configures the body scheme, and more than that, also influences the image of the material body. While the body scheme corresponds to the physical border given by the skin, he body image, in contrast, can be regarded as an idealised fiction of the self . This unified body image is very difficult to harmonise with the disassociated bodily sensations of the little baby. The gulf between the body image and the piece-meal physical sensations, which are always easily united by an imaginary self- constitution, shows that in this case body sensation and body image barely correspond to each other. The skin as an outer surface of the material body, perceived by sensory and physical means may suggest at first sight that there is a clear contour to the self, but it also shows up the gaps and splits in this supposed uniformity, as here the body image and body experience can never be made to fully coincide.
While in the imaginary image of the body and the self the skin serves as a visible border to the material body, one only becomes aware of the skin as an experienced border to the body at certain moments: when the self comes into contact with others (people or things), e.g. injures itself or is injured or experiences feelings of lust in erotic encounters. In the process every contact leaves visible and invisible traces on the skin: mementoes such as the etching of age into the skin in the form of lines and wrinkles, or as in scars as a sign of old wounds and vulnerability to injury. The skin is also a highly significant part of the material body, in which the individual history of a person materialises and leaves traces - the bodily self reveals itself through the skin as a threshold form of existence between nature and culture.
The skin as the border to the body takes on a self-constituting function, and this is not only through the projective casting of it and in the significance of the body as a visually perceptible form enveloped in skin, but further to that it requires the tactile stimuli, which uphold such an imaginary self-contouring of this kind: as the individual is stroked, touched and felt, and as it touches, feels and strokes itself, an unstable sense of one's own body beyond the visual impression develops: While vision leads to a stabilisation of the imaginary self-image, in the physical experience, this self-image is irritated again and again, and exposed as a ficitional construction.
IV Touch: Constant contact with the world
Touching the self and others by means of and through the skin are of decisive importance for the constitution of the self and equally for the exploration of the world around. In the process, every touch shows a dialogue structure, which results not only from the fact that we are always simultaneously touching and being touched, but also that every touch is always a silent answer to implicit demands and offers from the subject being touched. In this sense a person stands as a skin-enveloped being in constant, never-ending contact with the world, which effects certain impregnations, infections, and infusions, beyond explicit attitudes and conscious perceptions. These may be characterised as the experience of being penetrated by others, whose existence is felt even when the eye and ear have not noticed them. This shaping process which takes place through the tactile interaction with the world leads to a destabilisation of the rational self, confident in itself: "plunged into the stream of touch we are never master of ourselves, but in the nicest way we are maddened and decentered and for this very reason we are all the more full of life" . The imaginary self-image thus experiences a shock through every touch, as every physical contact takes place on the threshold between the self and the other, that is it is action and reaction in one. Activity and passivity, traditional dichotomies, melt into one another, as does the line between one person and another (whether human, animal or an object) becomes blurred for a moment in the touching and can only be re-established by reflective distancing. As a physical being, in the action of touch one is always simultaneously suffering and active, simultaneously identical with oneself and influenced by the other : every touch is a reaction of the body to that questioning atmosphere, which the opposite in each case exudes. The implicit character of effect and invitation of the person who is touched in each case shows that touches do not arise solely from purely subjective intentions, but are always guided in a certain direction by certain demands. In his later work, Merleau-Ponty  used the term Chiasmus to try and define the way in which every touch is seen to be a constant cross-over of the other and the own, which can only made explicit b a rational and linguistic order to a certain extent and which shows up the cracks and fissures in the structure of that order .
Touching the self in the sense of a tactile making sure of oneself is also affected by this cross-over. As transitive and intransitive moments are intertwined together in the action of touching ones own experienced body, an autoreflective doubling of the self occurs, which means that one is simultaneously subject and object. The discrepancy between sensation on ones own experienced body and a foreign body, which appears to become temporarily blurred in the action of touching oneself, shifts, as the skin as a perceived bordering sphere turns out to be more fluid and open than the clearly contoured visually perceptible skin border as the exterior of the body. But in fact this loss of borders is inherent in every touch: the central positioning and the anatomical demands of modern subjectivity can only be upheld - as can clearly be seen - by eliminating the tactile dimension (and in the end that of the experienced body at all).
Touch, therefore, always means a mixture of autonomy and heteronomy, an overlapping of self-determination and determination from outside. In the tactile approach to the world, which must be seen as an important area of discovery of the world, there is always a setting and a crossing of borders in equal measure: setting borders, because the physical self meets resistance in the contact with the other; crossing them, because every touch temporarily throws doubt on the reflective, self-constituting discrepancy between the self and the other. The recollection of the skin and the tactile approach to the world which is transmitted through it decentralise the traditional subject beyond all the investigations of discourse theory, on the level of its materiality, independent of the equally necessary reference to its embeddedness in a symbolic and social order. At the same time however, every tactile skin contact also enables the self to draw situated borders between itself and others, without which it could not exist - it is a constant balancing act between drawing up borders and crossing the borders, and through this process the decentered self re-contours itself again and again .
V Responsive Physicality as a Bordered and Borderless Horizon
What does the recourse to skin and touch mean for the attempt to create a new interpretation of the physical self? In the following chapter, I will present a concept of responsive physicality, with reference to new approaches in phenomenology, which are equally influenced by deconstructivist cognitive critique and by phenomenological traditions.
Referring to a concept of "responsive physicality" the following represents an attempt to redefine the physical self without either falling back onto traditional dichotomies and essentialisms or subscribing to an undifferentiated monism, as is latently suggested by the current visions of delimitation. In an outline of this, intertwining of the organic and the cultural dimensions which is constantly reconstituting itself is emphasised as is the fragility of the self which goes hand in hand with this.
In order to separate this from more culturalistic or discourse theory related positions, Waldenfels for example emphasises that in the unstoppable ageing processes, in pain as well as in illness we also see a level of resistance of the material, which reveals a remainder of the "etre sauvage " beyond cultural effects. This produces a gulf between subjective experience of the body and the organic experienced body. In addition Waldenfels  opposes theoreticians arguing from a more naturalistic or essentialistic positions, who believe that the last or main basis of all experience of being is to be found in the physical being. Instead of this we are referred here to the self-doubling, self-shifting, self-splitting of the experienced body, which is characteristic of the way of being of a physical self. This, via the skin or by touch, is in continual dialogue with the world around, and answers the demands of that world but also the interchange between the other and the own may be seen in the intimate relationship between self-reference and self-withdrawal.
The physical self, when viewed as a responsive self, is therefore always an answer to some other. The act exceeding the limits of the self which is associated with this is also to this extent always a crossing of the borders of the self, which leaves and exceeds the closed framework of the self in answering the demands of the other. It is a constant, open stream, an on-going interaction of action and re-action, but not reaction in the sense of a simple effect caused by some stimuli (behaviourism) but in the sense of an answer in the form of dialogue. So even as we become aware of our own sensual- physical experiences, a distancing from the self, an irrecoverable otherness with reference to the self takes place. The physical being therefore, in its sensual references to itself (seeing itself, hearing itself, touching itself) reveals a gulf, a non-coincidence in the coincidence, which cannot be covered over. So, the other, the inaccessible is also in the person himself or herself: as sensual experience which cannot be conceptually defined and as physical experience which defies any form of explication and categorization. The physical embeddedness in the world thus points to a moment of non-identicality, because neither reflection nor discourse can fully define the physical being-of-the-world. Self-constitution and the constitution of the Other, self-setting and determination of the other therefore reveal a continuous, on-going mixing up of the own and the other, which exposes the idea of an identity which is identical-with-itself or clearly contoured as an illusion and a fiction.
We have already seen above that every touch in its ambiguity reveals an irreconcilable otherness in self-reference. The demanding nature of things and situations, which make silent demands, to which the physical individual re- acts, opens up a space containing possible answers, an open horizon, which is bordering and borderless in one. The reaction to these silent offers of the opposite number in each case however, contains a blind spot, which we can describe as the blind spot in our answering behaviour. The things which we respectively answer in our behaviour with physical and linguistic forms of expression, are in the end in their very otherness inaccessible. The otherness shows itself both in the countenance, in the pose of the figure, in the embodied materiality of the other in each case, as well as in the anonymous discursive structures which shape us and as such are nonetheless recognisable and explicable only to a certain extent. The responsive discrepancy between that which we are answering and the answer we give results from this inaccessible otherness. The inaudible in the audible, the untouchable in the touchable, the invisible in the visible: we keep encountering dimensions of the otherness which we are subjected to because of this responsive physical embeddedness in the world and which permeates us ourselves. The recognition of these other demands shows that practice is always also heteropractice and speaking is always also answering; that is we live in the chiasmus between action on our own initiative, and exposure to outside forces.
So, through the skin and in every touch, it may be seen that we as physical beings are forced to allow the other its distance, the answering speaker its absence and indeterminacy and our actions their insufficiency. Asymmetry and shifting thus come to be seen as significant moments in our physical being-in-the-world. The unbridgeable gap between implicit functioning and explicit thematicising accordingly reveals a continuous inner discrepancy and an ambiguity, a doubling-up, which can lead the self into the labyrinths, cul- de-sacs and halls of mirrors of self- and reflective reference and make a unified self-awareness as an imaginary entity, effortlessly possible. Because in the clash of foreign demands and own answers there are irretrievable and insoluble gaps and splits, by which the physical and social self distinguishes itself.
By looking at the skin as a porous exterior to the body, which is a bordering outer cover of the self-image and a point of contact between the self and others in equal measure, the ambiguous threshold position of the embodied person becomes clear. Physical existence is as natural as it is cultural: polarisations, which attribute a primordial status to either one side or the other, fail to grasp this constantly shifting cross-over: A complete embodiment of the person, which would embed him or he in the laws and rhythms of nature, is as impossible as a complete debodiment or removal of the body, which would allow him or her to step outside of nature and would degrade this to the mere material of our ideas and actions.
However, if we interpret the physical self as a responsive existence, and therefore one which has always been a decentralised, threshold existence, then it may also be seen that in the context of new technological developments and the "post-human" and immaterial forms of identity and "Cyberpersonalities" which go along with these, any new interpretation of the self cannot avoid completely dispensing with the old dichotomies and discrepancies in favour of new perspectives of unifying and standardisation. Instead of striving for borderlessness in the sense of an undifferentiated amalgamation, where the gaps and breaks between nature and culture, organism and artefact, reality and virtuality would be simply negated, it is more a question of re-defining our concepts of body and self in the way as it has been done by Haraway and Hayles or as it can be found in performance art in virtual spaces, realised for example by artists like Diane Gromala, Gretchen Schiller and Jon McKenzie.
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 The expression "experienced body" (German Leib) is consciously used here to emphasise the distinction between this and the traditional understanding of a "material body". For, in contrast to common parlance, which assumes a separation of the material body (Körper) and the experienced body (Leib) and thus perpetuates the Cartesian separation in the face of statements suggesting otherwise, the body in the following text is taken to be an existence, which carries this duality within itself.
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Barbara Becker studied philosophy, sociology and history of arts. Her PhD relates to socio-philosophical problems of artificial intelligence and cognitive science. She worked as a research scientist for more than twenty years at several universities, in particular the German National Research Centre of Computer Science. Since 2001, she is a professor in media science at the University in Paderborn. Her current research focusses on cultural impacts of old and new media, methods of constructing body and identity by using media and media