One thing that writing the last post on Margrit Shildrick's Rethinking Prostheses talk has done is to get me thinking about that key question posed by Donna Haraway: "Why should our bodies end at the skin?". Or rather, it's got me thinking about it in more detail. I mentioned that this question in particular intrigued me in the context of the Human Computer Cyborg concept: I've always found it interesting the extent to which we engage with and utilise technology and our environment. However, this is very much a "systems perspective" - me thinking as an engineer. The notion that systems couple and uncouple to form new supersystems and subsystems is pretty inherent to the engineering mindset (more on this if I ever get round to reviewing Guru Madhaven's excellent "Think Like an Engineer" which is my current reading). One thing that did crop into my head though was the whole issue of the skin as a boundary, both physically and intentionally. These are thoughts in progress - I'm basically just throwing down what comes into my mind. Thinking out loud - or, er, thinking out visibly, at any rate.
Biology and Me
So, another caveat: I'm not a biologist. I dropped biology after doing GCSE dual-award science. I like physics and mathematics and mechanics: I like force diagrams, equilibria, calculus, equations of motion. I like the fact that a few fundamental principles build systematically on each other so that we can predict and model the behaviour of complex systems (with greater or lesser accuracy). Biology on the other hand (as I experienced it - maybe it's different as you go higher up) is all classifications and systems, and a soup of stuff that don't really tie logically together in my mind. I can't really explain it. You can ask my wife: she's a consultant geriatrician and the polar opposite of me in this respect. She likes classifications and symptoms and body systems and diagrams of organs, and really struggles with physics. It's like a whole different way of thinking: which may explain why she's a doctor and I'm an engineer, of course. I like biomechanics, though. That makes sense to me. A skeleton as a set of rigid body elements connected by actuated joints? Movement modelled using control theory? This I like. But I don't know much about the skin, so I may be completely wrong about all this. Feel free to let me know.
So, another caveat: I'm not a biologist. I dropped biology after doing GCSE dual-award science. I like physics and mathematics and mechanics: I like force diagrams, equilibria, calculus, equations of motion. I like the fact that a few fundamental principles build systematically on each other so that we can predict and model the behaviour of complex systems (with greater or lesser accuracy). Biology on the other hand (as I experienced it - maybe it's different as you go higher up) is all classifications and systems, and a soup of stuff that don't really tie logically together in my mind. I can't really explain it. You can ask my wife: she's a consultant geriatrician and the polar opposite of me in this respect. She likes classifications and symptoms and body systems and diagrams of organs, and really struggles with physics. It's like a whole different way of thinking: which may explain why she's a doctor and I'm an engineer, of course. I like biomechanics, though. That makes sense to me. A skeleton as a set of rigid body elements connected by actuated joints? Movement modelled using control theory? This I like. But I don't know much about the skin, so I may be completely wrong about all this. Feel free to let me know.
Unfortunately, the skin doesn't really feature in this reading. I've never done a model or a calculation where the skin was anything but a friction coefficient, with the annoying characteristic of being difficult to predict accurately (you might like to talk to my colleague Brian Henson who's done rather a lot on this!). So, in my engineering mindset, it's not difficult to conceive of a bit of extra mass or a longer rigid body, or of swapping bone for metal in hip replacements. There are huge practical issues to this integration, of course - but as a concept it's one that's easy for me to grasp. That makes the skin an interesting boundary.
The Five (plus) Senses
I was thinking about all this in the context of proprioception (the sense of where our body parts are relative to each other, even when we can't see them) as I was drawing up a control model for prehensile movements. Proprioception isn't tied in with the skin as far as I know - but it is contained within it. I mean, we have no proprioception for our hair, for example. That matters little to me these days, but in the days when I had hair reaching my waist, it wasn't too difficult to inadvertently lie down and trap it under it my shoulders because I didn't know that the sweeping it aside with my hand hadn't worked. Indeed, of the multitude of senses available, many (sensing temperature, vibrations, tasting, sense of balance, pain) rely on something interacting with or bypassing our skin. Even sight and sound rely on electromagnetic or airwaves being projected into our bodies. If I close my eyelids, no sight: if sound doesn't reach my ear drum, then I don't hear it. That's a very, very simplistic reading, of course, but it gives the jist. I don't have any external senses - the skin represents the limit of my ability to sense the world around me. It also represents the locus of my central nervous system's control. My skin represents the space envelope that I can project around me: I can adjust its shape and size and position by activating muscles and reorienting my skeleton, but if I want to exert forces on the world around me, they have to come through my skin. Again, this is very simplistic - biting, for example, would be a counter example. But for the most part, the skin is a good analogy for the physical boundary of the space I occupy, so it's not too surprising if we take it as the limit of a body.
I was thinking about all this in the context of proprioception (the sense of where our body parts are relative to each other, even when we can't see them) as I was drawing up a control model for prehensile movements. Proprioception isn't tied in with the skin as far as I know - but it is contained within it. I mean, we have no proprioception for our hair, for example. That matters little to me these days, but in the days when I had hair reaching my waist, it wasn't too difficult to inadvertently lie down and trap it under it my shoulders because I didn't know that the sweeping it aside with my hand hadn't worked. Indeed, of the multitude of senses available, many (sensing temperature, vibrations, tasting, sense of balance, pain) rely on something interacting with or bypassing our skin. Even sight and sound rely on electromagnetic or airwaves being projected into our bodies. If I close my eyelids, no sight: if sound doesn't reach my ear drum, then I don't hear it. That's a very, very simplistic reading, of course, but it gives the jist. I don't have any external senses - the skin represents the limit of my ability to sense the world around me. It also represents the locus of my central nervous system's control. My skin represents the space envelope that I can project around me: I can adjust its shape and size and position by activating muscles and reorienting my skeleton, but if I want to exert forces on the world around me, they have to come through my skin. Again, this is very simplistic - biting, for example, would be a counter example. But for the most part, the skin is a good analogy for the physical boundary of the space I occupy, so it's not too surprising if we take it as the limit of a body.
Inner Space
A knee or hip replacement represents a clear crossing of the skin as a boundary, but doesn't change its nature. It swaps bone for metal, polymer and plastic. It seems reasonable to assume that these are subsumed into the person: though whether recipients feel that way is a different matter. The implant is clearly within the body, unlike an externally attached prosthetic: it's removal and replacement is nontrivial. Getting through the skin is a major event.
A knee or hip replacement represents a clear crossing of the skin as a boundary, but doesn't change its nature. It swaps bone for metal, polymer and plastic. It seems reasonable to assume that these are subsumed into the person: though whether recipients feel that way is a different matter. The implant is clearly within the body, unlike an externally attached prosthetic: it's removal and replacement is nontrivial. Getting through the skin is a major event.
This raises another significant factor - namely the problem of piercing the skin. The skin is our first layer of defence - once broken, the way is open to many infections: a risk to any operation. Also, within the body, any outside material can be subject to rejection. The immune system can take exception: implanted sensors become fouled and damaged. It's not impossible to circumvent this, but the reality is that changes under the skin present a different challenge to those outside. Again, the skin represents a clear delineation between internal and external environments.
Body Modification
Another objection might be the issue of body modification: Tattoos and piercings. Not, I suppose, cosmetic surgery, since this might be taken to change the skin, rather than the inner or outer environments; implants are I suppose covered by the discussion above.
Another objection might be the issue of body modification: Tattoos and piercings. Not, I suppose, cosmetic surgery, since this might be taken to change the skin, rather than the inner or outer environments; implants are I suppose covered by the discussion above.
I know little of body modification, having no tattoos or piercings, and never feeling any desire for them, so my scope for discussion is limited and I could be way off the mark. I suppose, though, that piercings rely on reshaping the skin; tattoos might come under implants, though they are a little different in the sense of residing in the skin rather than under it. Thus, the skin marks a natural, clearly defined, objective, physical system boundary for defining the limits of the body and person. What objections could there be?
Hair, Nails and Whiskers
Of course, the hair and nails are body parts that reside outside the skin. We cut both off in a way we would not other parts of our body: they have no sensation, and we don't control them directly. But we would, I think, instinctively recognise them as part of the body. If someone shaved your head, or cut off your ponytail, would this be seen as the same as ripping someone's shirt? Or something more personal? Whiskers are another interesting example - outside the body, but used for sensing.
Of course, the hair and nails are body parts that reside outside the skin. We cut both off in a way we would not other parts of our body: they have no sensation, and we don't control them directly. But we would, I think, instinctively recognise them as part of the body. If someone shaved your head, or cut off your ponytail, would this be seen as the same as ripping someone's shirt? Or something more personal? Whiskers are another interesting example - outside the body, but used for sensing.
Disassembly
Perhaps the most compelling argument for the skin defining our bodies is related to the issue of assembly (or assemblage, as discussed by Margrit Shildric - see my post on her talk). Fundamentally: disassembling anything within our skin causes injury.
From a systems perspective, the skin delimits a system that is difficult to subdivide. I can remove my clothes and put on other clothes; I can pick up different tools; climb into or out of a car, with much less effort and risk than I could remove my arm, or my kidneys. There's a pretty clear difference there. Even disassembling a tattoo from the body is painful and time-consuming. Compare that with a transfer which stays firmly outside the skin.
A recent tweet from Open Bionics really brought this home to me. It concerns the recipient of the first hand transplant (or hands transplant, since both hands were replaced), who now wants them removed. This raises two interesting issues: first, it again raises the equivalence between transplants and prostheses as ways to replace or augment body parts. Secondly, it highlights the issue of the skin as a boundary: once grafted on, the hands are difficult and risky to remove in a way that prosthetic hands are not. The same holds for a heart bypass, a pacemaker, an artificial hip. Once inside the skin, these things are very difficult to remove.
Perhaps the most compelling argument for the skin defining our bodies is related to the issue of assembly (or assemblage, as discussed by Margrit Shildric - see my post on her talk). Fundamentally: disassembling anything within our skin causes injury.
From a systems perspective, the skin delimits a system that is difficult to subdivide. I can remove my clothes and put on other clothes; I can pick up different tools; climb into or out of a car, with much less effort and risk than I could remove my arm, or my kidneys. There's a pretty clear difference there. Even disassembling a tattoo from the body is painful and time-consuming. Compare that with a transfer which stays firmly outside the skin.
A recent tweet from Open Bionics really brought this home to me. It concerns the recipient of the first hand transplant (or hands transplant, since both hands were replaced), who now wants them removed. This raises two interesting issues: first, it again raises the equivalence between transplants and prostheses as ways to replace or augment body parts. Secondly, it highlights the issue of the skin as a boundary: once grafted on, the hands are difficult and risky to remove in a way that prosthetic hands are not. The same holds for a heart bypass, a pacemaker, an artificial hip. Once inside the skin, these things are very difficult to remove.
In summary, then: there are several good reasons to take the body as ending at the skin:
1. The skin represents the boundary of one's senses and actions. We can't sense anything that doesn't have some way of reaching the space envelope of the skin (including reflected light and sound - after all, eyes and ears are within this space) and we can't anything except through the intermediary of the skin (sound and breath being exceptions, but these originate within rather than without the envelope defined by the skin). Even a tool or instrumented which permits remote sensing or action then has to communicate to the body.
2. Removing things once they are within the skin is inherently more difficult than things without. The skin as a system boundary encompasses a system that is difficult to subdivide. Systems external to the skin are easier to assemble and disassemble with than those within the skin.
3. That very difficulty renders it more objective - it provides a physical definition of the space a person occupies, and a physical system boundary. You don't need to argue about which bits are in you and which are in someone else.
So it's pretty clear that our bodies end at the skin. Or is it?
Queering the Deal
There are a few interesting counterexamples. Of course, you can probably get into questions about what defines a body as opposed to what defines a person. I'm sure smarter minds than mine have grappled with exactly this, so bear with me if this is very basic.
There are a few interesting counterexamples. Of course, you can probably get into questions about what defines a body as opposed to what defines a person. I'm sure smarter minds than mine have grappled with exactly this, so bear with me if this is very basic.
Firstly: robotic prosthetics are a very interesting case. Take a look at Open Bionics' Ada hand (or any of their jazzy variants, for that matter!). It has sensors and actuators, and intelligence. It uses EMG to control it - reading signals sent to the muscles by the CNS. Admittedly, it doesn't feed back to the CNS, and it reads across the skin, but still. Colleagues at the University are working on stimulating nerve endings using vibrations to produce sensations for remote touch. Again, without breaking the skin, but still - once these are being controlled directly by the CNS, the boundary with the body blurs. A lot.
Secondly, there is a practical consideration. I was struck by Sir Bert Massie CBE's post about the AT Hub, discussing the perils of compartmentalising AT. If you take the skin as the limit of the person, you miss the fact that many such devices aren't optional extras, but essential to their wellbeing, and if they are removed, damaged, or rendered unusable by circumstances, the consequences are just as disabling as losing part of the body. I'm talking out of turn there: making inferences from what I read, and about which I have little meaningful experience. And it almost certainly wasn't Sir Bert's intention to raise issues about the definition of the body, rather about the importance of communication and integration between stakeholders in AT and hence the need for the AT Hub.
But it's an interesting issue, and important to the conception of the body and the self. In summary - there are some pretty good reasons to take the skin as a special boundary and as defining the limits of the body. But there are some practical reasons to extend that concept, and new technologies that rather blur the boundaries.
Anyway - these are just my musings: thinking out loud. Feel free to let me know your thoughts.
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