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<strong>Network</strong> logic<br />

Boundaries <strong>of</strong> identity<br />

All living organisms have a physical boundary that discriminates<br />

between the system – the ‘self’, as it were, and its environment. Cells,<br />

for example, are enclosed by membranes and vertebrate animals by<br />

skins. Many cells also have other boundaries besides membranes,<br />

such as rigid cell walls or capsules, but only membranes are a<br />

universal feature <strong>of</strong> cellular life. Since its beginning, life on Earth has<br />

been associated with water. Bacteria move in water, and the<br />

metabolism inside their membranes takes place in a watery<br />

environment. In such fluid surroundings, a cell could never persist as<br />

a distinct entity without a physical barrier against free diffusion. The<br />

existence <strong>of</strong> membranes is therefore an essential condition for cellular<br />

life. 5<br />

A cell membrane is always active, opening and closing continually,<br />

keeping certain substances out and letting others in. In particular, the<br />

cell’s metabolic reactions involve a variety <strong>of</strong> ions, and the membrane,<br />

by being semi-permeable, controls their proportions and keeps them<br />

in balance. Another critical activity <strong>of</strong> the membrane is to continually<br />

pump out excessive calcium waste, so that the calcium remaining<br />

within the cell is kept at the precise, very low level required for its<br />

metabolic functions. All these activities help to maintain the cellular<br />

network as a distinct entity and protect it from harmful<br />

environmental influences. The boundaries <strong>of</strong> living networks, then,<br />

are not boundaries <strong>of</strong> separation but boundaries <strong>of</strong> identity.<br />

Social networks<br />

The main goal <strong>of</strong> my research over the past ten years has been to<br />

extend the systemic conception <strong>of</strong> life to the social domain, and in my<br />

last book, The Hidden Connections,I discuss this extension in terms <strong>of</strong><br />

a new conceptual framework that integrates life’s biological, cognitive<br />

and social dimensions. 6 My framework rests on the assumption that<br />

there is a fundamental unity to life, that different living systems<br />

exhibit similar patterns <strong>of</strong> organisation. This assumption is supported<br />

by the observation that evolution has proceeded for billions <strong>of</strong> years<br />

by using the same patterns again and again. As life evolves, these<br />

28 Demos

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