computational boundary of the self notion is simply a way to try to be able to think about very diverse kinds of uh beings diverse kinds 00:08:12 of intelligences all all on one scale

it's easy for us to look at us and think okay we're 30 trillion human cells give or take we're about 39 trillion bacterial cells at what point do we consider ourselves bacteria or at what point do we consider ourselves 00:07:46 human

an overview of the paper

the computational boundary of a self

this is now quantifying this this safe space but for the first time also doing it for justice so measuring the maximum allowed 00:15:33 of significant harm to people and the key take home here is the following in the outer ring here the red and green you see the safe boundary definitions 00:15:45 the blue lines are the assessment of justice so not surprisingly if we care about people the safe bound is about the stability of the planet but if we care about avoiding significant harm to hundreds of millions of people across 00:15:58 the world the climate boundary shrinks from 1.5 down to one degree

. „Klimamodellen zufolge hat der Grundwasserbestand in der Zeit von 1993 bis 2010 um 2.150 Gigatonen abgenommen“, berichten Seo und seine Kollegen. Anhand eines Modells sowie Schwerefeldmessungen und Daten zur Polwanderung haben sie rekonstruiert, wie sich dies auf die Bewegung der Erdachse ausgewirkt hat.

Rose therefore recommended "explicit consistency checks in a protocol ... even if they impose implementation overhead".

1.5 degrees Celsius is the safe boundary this aligns with the intergovernmental panel on climate change with one difference we emphasize that this is a physical limit push it beyond that point 00:05:23 and we risk permanent damage on societies and the world economy

finally the boundary on air pollution on aerosols a boundary which we today have scientific evidence that it actually has 00:07:02 impacts on regulating the state of the atmosphere and the hological cycle pushing the monsoon systems in the southern hemisphere particularly into less rainfall

fertilizer use one of these boundaries that are today overloading and causing dead zones pollutants also 00:06:38 greenhouse gas massive implications on water quality and coastal zones we quantify here at the global level the maximum allowed loading of reactive nitrogen and reactive phosphorus used 00:06:50 predominantly in fertilizer systems

third boundary is on fresh water here we have two boundaries one is that 00:06:14 we have to keep at least 20 percent of natural flows and rivers intact for ecosystem services in aquatic systems the second is very basic on groundwater that extraction of groundwater levels 00:06:25 must be less than the recharge levels across the world on fertilizer use one of the

we are today concluding that we're outside even of the just boundary on climate

within the next decade we are at risk of pushing ourselves outside of the safe 00:10:15 boundary of 1.5 degrees Celsius

on the biosphere we're also outside of the safe and just boundaries which is already recognized 00:10:27 in the Kunming in Montreal cbd15 of the necessity of halting and reversing the loss of biodiversity by 2030 which entirely aligns with the Earth commission's assessment that we now need to keep 50 to 60 percent of the Earth's 00:10:41 surface intact this means from now onwards zero loss of intact nature across the world economy

the biosphere is a fundamental basis for all human well-being and we have two 00:05:36 boundaries defined for the biosphere the first one is the conclusion that at least 50 to 60 percent of intact nature must be remained on Earth to be able to 00:05:48 support the world economy and the resilience of the entire Earth system the second boundary is for all the managed land agriculture forestry urban areas that at least 25 percent of every 00:06:00 square kilometer has to have natural levels of fluorine fauna to be able to remain healthy and support the economy

First, consider who gets to make the rules. Tenured scholars who, as we’ve noted, are mostly white and male, largely make the rules that determine who else can join the tenured ranks. This involves what sociologists call “boundary work,” or the practice of a group setting rules to determine who is good enough to join. And as such, many of the rules established around tenure over the years work really well for white scholars, but don’t adequately capture the contributions of scholars of color.

Research is needed to determine the situations in which the redundancy principle does not hold

boundary conditions.

For Plessner, the living boundary is both a liminal zone that mediates between organism and the outer medium, itself being neither, and yet also an enactively self-defining and enforcing circumference and outer-limit. The organism moves outward in the expansion and assimilation of its liminal zone and moves inward, taking the outer within, re-establishing itself and reasserting its perimeter. The living boundary already introduces a subject-object status that prefigures for Plessner the overcoming of dualisms between inner and outer, interiority and exteriority. The living boundary is an on-going enactment of an exteriority that it defines and yet also reaches into and assimilates and of an interiority that is both sustained and transformed. The motive force of the dynamic living state is this double aspectivity of its existence and the dialectical tension which drives it forward.

Pace Dilthey, Plessner's "Levels" is not about interpreting historical contingencies, nor about the more familiar evolutionary sedimentation of frozen accidents, but rather is about looking to establish transcendental conditions (or categories) of biotic possibility that he refers to as "modals of the organic." As with Hegel he challenges us with a proposed logic of life always mobilized by dialectical tensions, albeit not on the basis of any form of idealism and bereft of a Hollywood ending. For Plessner, that which is both the sine qua non of the living state and that generative 'principle' from which organic modals can be derived is the on-going performance of a self-positioning boundary, and it is highly unlikely that anybody has ever thought as deeply about the implications of what this means.

Such boundary objects play a brokering role involving translation, coordination, and alignment among the perspectives of different communities coming together in a kind of meta-community [26], which is the case in our fractalized community networks.

boundary objects

Special case check = Non-obvious, non-boundary special values, for example log(1 + the smallest floating point number).

Edge / Boundary check = The maximum or minimum input which is expected to produce correct output

rethink the intricate, and increasingly inti-mate, configurations of the human and the machine.

sociocultural factors

hus, we believe challenges occur in all three indica-tors of the level of development of a TMS—expertisespecialization, credibility, and expertise coordination—requiring a need to consider extending theorizing abouteach indicator for emergent response groups.

third response to manage tensions is to promoteknowledge collaboration by enacting dynamic bound-aries. In social sciences, although boundaries divide anddisintegrate collectives, they also coordinate and inte-grate social action (Bowker and Star 1999, Lamont andMolnár 2002). Fluidity brings the need for flexible andpermeable boundaries, but it is not only the propertiesof the boundaries but also their dynamicity that helpmanage tensions.

Based on our collective research on to date, we haveidentified that as tensions ebb and flow, OCs use (or,more precisely, participants engage in) any of the fourtypes of responses that seem to help the OC be gen-erative. The first generative response is labeledEngen-dering Roles in the Moment. In this response, membersenact specific roles that help turn the potentially negativeconsequences of a tension into positive consequences.The second generative response is labeledChannelingParticipation. In this response, members create a nar-rative that helps keep fluid participants informed ofthe state of the knowledge, with this narrative havinga necessary duality between a front narrative for gen-eral public consumption and a back narrative to airthe differences and emotions created by the tensions.The third generative response is labeledDynamicallyChanging Boundaries. In this response, OCs changetheir boundaries in ways that discourage or encouragecertain resources into and out of the communities at cer-tain times, depending on the nature of the tension. Thefourth generative response is labeledEvolving Technol-ogy Affordances. In this response, OCs iteratively evolvetheir technologies in use in ways that are embedded by,and become embedded into, iteratively enhanced socialnorms. These iterations help the OC to socially and tech-nically automate responses to tensions so that the com-munity does not unravel.

Fluidity recognizes the highly flexible or permeableboundaries of OCs, where it is hard to figure out whois in the community and who is outside (Preece et al.2004) at any point in time, let alone over time. Theyare adaptive in that they change as the attention, actions,and interests of the collective of participants change overtime. Many individuals in an OC are at various stagesof exit and entry that change fluidly over time.

Recently, Brown and Duguid (2001, p. 208) sug-gested that coordination of organizational knowledgeis likely to be more challenging than coordination ofroutine work, principally because the “elements to becoordinated are not just individuals but communitiesand the practices they foster.” As we found in ourinvestigation of coordination at the boundary, signif-icant epistemic differences exist and must be recog-nized. As the dialogic practices enacted in responseto problematic trajectories show, the epistemic dif-ferences reflect different perspectives or prioritiesand cannot be bridged through better knowledge

Boundarywork requires the ability to see perspectives devel-oped by people immersed in a different commu-nity of knowing (Boland and Tenkasi 1995, Star andGriesemer 1989). Often, particular disciplinary focilead to differences in opinion regarding what stepsto take next in treating the patient.

The termdialogic—as opposed to monologic—recognizes dif-ferences and emphasizes the existence of epistemicboundaries, different understandings of events, andthe existence of boundary objects (e.g., the diagnosisor the treatment plan). A dialogic approach to coordi-nation is the recognition that action, communication,and cognition are essentially relational and highlysituated. We use the concept of trajectory (Bourdieu1990, Strauss 1993) to recognize that treatment pro-gressions are not always linear or positive.

In knowledge work, several related factors sug-gest the need to reconceptualize coordination.

signifies a new epistemology insofar as it portraysevents as discrete and isolated; knowledges as mod-ifiable, categorizable, and abstractable; and locally-situated knowledges as best understood by thoseworking remotely

. Previously, scholars have generally ignored any notion of time. Now, we need to make explicit our use of time in understanding disaster. Such an application, I believe, will give us a much deeper understanding on defining disaster, how and why such events unfold, and how various social entities attempt to return to normal after the event. Finally, the use of social time in disaster can provide sociologists a deeper look into understanding key theoretical issues related to social order, social change and social emergence, along with voluntaristic versus deterministic patterns of behavior among various units of analysis.

the field. Such a fresh approach possibly improves a wide range of conceptual issues in disasters and hazards. In addition, such an approach would give us insights on how disaster managers, emergency responders, and disaster victims (recognizing that these “roles” may overlap in some cases) see, use and experience time. This, in turn, could assist with a number of applied issues (e.g., warning, effective “response,” priorities in “recovery”) throughout the process of disaster.

The next logical step to aid analysis would be to cross-tabulate the temporal periods of "before, during, and after" with functional activities. This type of analysis and consideration could be further extended by including both the unit of analysis and various social categories such as social class or ethnicity. This type of three-dimensional approach would also strongly highlight the idea that disaster phases are multilayered. Overall, not only do different groups and units of analysis experience the phases at different times, but that multiple aspects of time (i.e., objective and subjective; before, during, after a disaster) intermesh with specific activities.

We must differentiate whether the use of any phrase refers to temporal or functional aspects of disaster. They should not have multiple meanings

Second, the manner the field handles the issue of disaster phases actually reflects a larger problem in the field. Specifically, how do we define disaster? Kreps (1984, p. 324) comes closest to recognizing the relationship among disaster phases, the theoretical components of disaster (i.e., social order and social action), and the definition of disaster (primarily in a heading in his paper). Unfortunately, he does not elaborate upon the connection of defining disaster and disaster phases. Thus, recognizing and recasting our notion of disaster phases may actually help the field more precisely understand or define "disaster."

Mileti, Drabek, and Haas developed their six categories of: 1) preparedness/adjust­ment; 2) warning; 3) pre-impact, early actions; 4) post-impact, short-term actions; 5) relief or restoration, and 6) reconstruction. They justify these categories by noting that "Numerous researchers have documented how activities and nonnative definitions appear to vary across time and vary greatly among events" (Mileti, Drabek, Haas 1975, p. 9). The six phases serve as a central component of the authors' codification effort (it organizes the book chapters). Yet, the authors do not provide a more specific defini­tion for each category. Other theoretical underpinnings in the book receive much more detailed justification (e.g., collective stress, social nature of disaster).

Under the stress of the situation, with too many peopledoing too many things at once, the socio-technical infrastructure that underliestheirwork practice wasbreaking down. Star and Ruhleder [25] explain that infrastructure becomes visible only at these points of breakdown. Volunteers directedtheir attention to their social configuration as the critical infrastructure here (the technical infrastructure remains take

It is boundaries that help us separate one entity from another: "To classify things is to arrange them in groups ... separated by clearly determined lines of demarcation .... At the bottom of our conception of class there is the idea of a circumscription with fixed and definite outlines. "7 Indeed, the word define derives from the Latin word for boundary, which is finis. To define something is to mark its boundaries, 8 to surround it with a mental fence that sepa­rates it from everything else. As evidenced by our failure to notice objects that are not clearly differentiated from their surroundings, it is their boundaries that allow us to perceive "things" at all.

es an entity with a distinctive meaning5 as well as with a distinctive identity that sets it apart from everything else. The way we cut up the world clearly affects the way we organ

Nonetheless, without some lumping, it would be impossible ever to experience any collectivity, or mental entity for that matter. The ability to ignore the uniqueness of items and regard them as typical members of categories is a prerequisite for classifying any group of phenomena. Such ability to "typify"106 our experience is therefore one of the cornerstones of social reality

A mental field is basically a cluster of items that are more similar to one another than to any other item. Generating such fields, therefore, usually involves some lumping.

A frame is characterized not by its contents but rather by the distinctive way in which it transforms the contents' meaning.

Temporal differentiation helps substantiate elusive mental dis­tinctions. Like their spatial counterparts, temporal boundaries often represent mental partitions and thus serve to divide more than just time.

In order to endow the things we perceive with meaning, we normally ignore their uniqueness and regard them as typical mem­bers of a particular class of objects (a relative, a present), acts (an apology, a crime), or events (a game, a conference).2 After all, "If each of the many things in the world were taken as distinct, unique, a thing in itself unrelated to any other thing, perception of the world would disintegrate into complete meaninglessness. "3 Indeed, things become meaningful only when placed in some category.

The perception of supposedly insular chunks of space is probably the most fundamental manifestation of how we divide reality into islands of meaning. Examining how we partition space, therefore, is an ideal way to start exploring how we partition our social world

These protocols, formal structures, plans, procedures, and schemes can be con-ceived of asmechanismsin the sense that they (1) are objectified in some way(explicitly stated, represented in material form), and (2) are deterministic or at leastgive reasonably predictable results if applied properly. And they aremechanisms ofinteractionin the sense that they reduce the complexity of articulating cooperativework.

In this section of the paper we broach two aspects of this articulation issue, onefocusing on the management of workflow, the other on the construction and manage-ment of what we term a ‘common information space’. The former concept has beenthe subject of discussion for some time, in the guise of such terms as office automa-tion and more recently, workflow automation. The latter concept has, in our view,been somewhat neglected, despite its critical importance for the accomplishmentof many distributed work activities

Resistance Realily is 'that which resists,' according to Latour's (1987) Pragmatist­inspired definition. The resistances thal designers and users encounter will change lhc ubiquitous networks of classifications and standards. Although convergence may appear at times to create an inescapable cycle of feedback and verification, the very multiplicity of people, things and processes involved mean lhat they are never locked in for all time.

Infrastructure and Method: Convergence These ubiquitous, textured dai;sifications and standards help frame our representation of the past and the sequencing of event� in the present. They (:an best be understood as doing the ever local, ever partial work of making it appear that science describes nature (and nature alone) and that politics is about social power (and social power alone).

Practical Politics �1 ·he fourch major theme is uncovering the practical politics of classifying awl standardizing. 'fhi<; is the de.sign end of the spectrum of investigat­ing categories and standards as technologies. There are two processes associated with these politics: arriving at categories and standards, and, along the way, deciding what will be visible or invisible within the system.

The Indeterminacy of the Past: Multiple Times, Multiple Voices The third methodological theme concerns ihe f1asl as indetc,rr,1inate. 10 We are constantly revising our knowledge of the past in light of new developments in the present.

Materiality and Texture The second methodological departure point is that. classifications and standards are material, as well as symbolic.

This categorical saturation furthermore forms a complex web. Al­though it is possible to pull out a single dassilication scheme or stan­dard for reference purposes, in reality none of them stand alone. So a subproperty of ubiquity is interdependence, ,md frequently, integration. A systems approach might see the proliferation of both standards and classilications as purely a matter of integration-almost like a gigantic web of interoperability. Yet the sheer density of these phenom­ena go beyond questions of interoperability. They are layered, tangled, textured; they interact lo form an ecology as well as a flat set of compatibilities.

Ubiquity The first major theme is the ubiquity of classifying and standardizing. Classification schemes and standards literally saturate our environ­ment.

A definition of infrastructure

This chapter offers four themes, methodological points of departure for the analysis of these complex relationships. Each theme operates as a gestalt switch-it comes in the form of an i11fras/:ruclural inversion (Bowker 1994). This inversion is a struggle against the tendency of infrastructure to disappear (except when breaking down). Tt means learning to look closely at technologies and arrangements that, by design and hy habit, tend to fade into the woodwork (sometimes literally!). Infrastructural inversion means recognizing the depths of interde­pendence of technical networks and standards, on the one hand, and the real work of politics and knowledge production8 on the other.

Standards Classifications and standards are closely related, but not identical. \-Vhile this book focuses on classificalion, standards are crucial compo­nents of the larger argument. The systems we discuss often do become standardized; in addition, a standard is in part a way of classifying the world. What then are standards? The term as we use it in the book has several dimensions:

Infrastructures are never transparent for everyone, ancl lheir '\\•ork­abilit y as they scale up becomes increasingly complex. Through due methodological attention to the architecture and use of these syslems, we can achieve a deeper understanding of how it is that individuals and communities meet infrastructure. ·we know that this means, at Lhe leasl, an understanding of infraslructure that includes these points:

The sheer density of the collisions of classification schemes in our lives calls for a new kind of science, a new set of metaphors, linking tradi­tional social science and computer and information science. We need a tqpography of things such as the distribution of ambiguity; the fluid dynamics of how classification systems meet up-a plate tectonics rather than a static geology. This nevi science will draw on the best empirical studies of work-arounds, information use, and mundane tools such as desktop folders and file cabinets (perhaps peering back­wards out frorn the Web and into the practices). It will also use the best of object-oriented programming and other areas of computer science to describe this territory. It will build on years of valuable research on classification in library and information s<:ience.

Information infrastrucLUre is a tricky thing to analyze_l; Good, usable systems disappear almost by deiinition. The easier they arc lo use, the harder they are to see.

A� we know from studies of work of all sorts, people do not do the ideal joh, but the doable job. \Vhen faced with too many alternatives and too much information, they satisfice (Mard1 and Simon 1958).

Forms like Lhe death certificate, ·when ag6TTcgated, form a case of what Kirk and Kutd1ins (1992) call "the substitution of precision for validity" (see also Star 1989b). That is, when a seemingly neutral data collection mechanism is substituted for ethkal conflict about the con­tents of the forms, the moral debate is partially erased. One may get ever more prn:ise knowledge, without having resolved deeper ques­tions, and indeed, by burying those questions.

we ·define boundary o4_jects as those o�jects that both inhabit several communities of practice and satisfy the informational requirements of each of them. In working practice, tJ1ey are objects that are able both to travel across borders and maintain some sort of constant identity. They can be tailored to meet rhe needs of any one community (they arc plastic.: in this sense, or customizable). At the same time, they have common identities across settings. 'Ibis is achieved by aJlowing the objects to be weakly struc­tured in wmmon use, imposing stronger structures in the individual­site cailored use. They a.re thus both ambiguous and constant; they may be abstract or concrete.

Classifications may or may not become standardized. If they do not, they are ad hoc, limited to an individual or a local community, and/or of Limited duration. At the same time, every successful standard imposes a classification system, al the very least between good and bad ways of organizing acLions or things. And the work-arounds involved in the practical use of standards frequently entail the use of ad hoc nonstandard categories.

Nomenclature and dassifi<:at..ion are frequently confused, howevc1; since attempts are often made to model nomencla­ture on a 1>ingle, stable system of classification principles, as for exam­ple with bot.any (Bowke1; in press) or anatomy.

Clas.�ification A classification is a spatial, temporal, or sjH1ti11-lemporal segmm,tation rif lhe world. ,\ "classification system" is a set of boxes (rnelaphorical or literal) inlo which things can be pul to then do some kind of work-bureau­cratic or knowledge production. In an abstract, .ideal sense, a classifica­tion system exhibits the frillowing properties:

vVe have a moral and ethical agenda in our querying of these systems. Each standard and each category valorizcs some point of view and silences another. This is not inherently a bad thing-indeed it is inescapable.

Table 1.1 A definition of infrastructure

This categorical saturation furthermore forms a complex web. Al­though it is possible to pull out a single classification scheme or stan­dard for reference purposes, in reality none of them stand alone. So a_ subproperty of ubiquity is interdependence, and frequently, integra­t10n. A systems approach might see the proliferation of both standards and classifications as purely a matter of integration-almost like a gigantic web of interoperability. Yet the sheer density of these phenom­ena go beyond questions of interoperability. They are layered, tangled, textured; they interact to form an ecology as well as a flat set of compatibilities.

Ubiquity __ The first major theme is the ubiquity of classifying and standardmng. Classification schemes and standards literally saturate our environ­ment.

This chapter offers four themes, methodological points of departure for the analysis of these complex relationships. Each theme operates as a gestalt switch-it comes in the form of an infrastructural inversion (Bowker 1994). This inversion is a struggle against the tendency of infrastructure to disappear (except when breaking down). It means learning to look closely at technologies and arrangements that, by design and by habit, tend to fade into the woodwork (sometimes literally!). Infrastructural inversion means recognizing the depths of interde­pendence of technical networks and standards, on the one hand, and the real work of politics and knowledge production8 on the other.

Infrastructures are never transparent for everyone, and their work­ability as they scale up becomes increasingly complex. Through due methodological attention to the architecture and use of these systems, we can achieve a deeper understanding of how it is that individuals and communities meet infrastructure. We know that this means, at the least, an understanding of infrastructure that includes these points:

Information infrastructure is a tricky thing to analyze.6 Good, usable systems disappear almost by definition. The easier they are to use, the harder they are to see. As well, most of the time, the bigger they are, the harder they are to see.

The sheer density of the collisions of classification scheme� in_ our liv�s calls for a new kind of science, a new set of metaphors, hnkmg tradi­tional social science and computer and information scien�e. We ne�d a topography of things such as the distribution of ambiguity; the flu_,d dynamics of how classification systems �eet u�-a plate tectomcs rather than a static geology. This new science will draw on the best empirical studies of work-arounds, info�mation use, and �undan_e tools such as desktop folders and file cabmets (perhaps peering back­wards out from the Web and into the practices). It will also use th<: best of object-oriented programming and other areas of compute, science to describe this territory. It will build on years of valuablt research on classification in library and information science.

s we know from studies of work of all sorts, people do not do the ideal job, but the doable job. When faced with too many alternatives and too much information, they satisfice (March and Simon 1958).

Forms like the death certificate, when aggregated, form a case of what Kirk and Kutch ins ( 1992) call "the substitution of precision for validity" (see also Star 1989b). That is, when a seemingly neutral data collection mechanism is substituted for ethical conflict about the con­tents of the forms, the moral debate is partially erased. One may get ever more precise knowledge, without having resolved deeper ques­tions, and indeed, by burying those questions.

we define boundary objects as those objects that both inhabit several communities of practice and satis� the informational requirements of each of them. In working practice, they are objects that are able both to travel across borders and maintain some sort of constant identity. They can be tailored to meet the needs of any one community (they are plastic in this sense, or customizable). At the same time, they have common identities across settin�s. This is achieved by allowing the objects to be weakly struc­tured m common use, imposing stronger structures in the individual­site tailored use. They are thus both ambiguous and constant; they may be abstract or concrete.

Classifications may or may not become standardized. If they do not, they are ad hoc, limited to an individual or a local community, and/or of limited duration. At the same time, every successful standard imposes a classification system, at the very least between good and bad ways of organizing actions or things. And the work-arounds involved in the practical use of standards frequently entail the use of ad hoc nonstandard categories.

Standards Classifications and standards are closely related, but not identical. While this book focuses on classification, standards are crucial compo­nents of the larger argument. The systems we discuss often do become standardized; in addition, a standard is in part a way of classifying the world.

Nomenclature and classification are frequently confused, however, since attempts are often made to model nomencla­ture on a single, stable system of classification principles,

Classification A classification is a spatial, temporal, or spatio-temporal segmentation of the world. A "classification system" is a set of boxes (metaphorical or literal) into which things can be put to then do some kind of work-bureau­cratic 9r knowledge production.

We have a moral and ethical agenda in our querying of these systems. Each standard and each category valorizes some point of view and silences another.

Members of organizations sometimes have differing (and multiple)goals, and conflict may be as important as cooperation in obtaining is-sue resolutions (Kling, 1991). Groups and organizations may not haveshared goals, knowledge, meanings, and histories (Heath & Luff,1996; Star & Ruhleder, 1994).

empirical literature on organizational time has extended research on time as a control variable of boundary condition (George & Jones, 2000; Langley, Smallman, Tsoukas, & Van de Ven, 2013)

And the determination of organizational age illustrates the constructed, enacted nature of the past, because what at first glance seems like a simple, even objective matter becomes ambiguous when mergers and acquisitions are involved. Is the founding date the date that the oldest of the merger partners began operations, or is it the date when the last partners merged? Families can face the same ambiguities when one or both spouses have been married previously and they and their children combine to form new families. As the definition of the situation principle teaches (see Chapter 1), the important is­sue is when the people in the organization or family believe it was founded.

4.

According tothe Healthcare Hashtag Project, there are 3,646 hashtags for 8,710health topics, as of January 2014.

However much a boundary, it is always a permeable membrane between self and other.