Increasingly, the word turns basic, its capillary complexity beaten out. A membrane gets you a dead, hermetic sheath: synthetic sheeting to insulate a building from moisture or fire; a plastic barrier against infection.
This may in fact be the most venerable meaning. Across history, the most impressive quality of skin and tissue – membrana – was impermeability. Leather, which could be used for carrying liquid or keeping out the rain, was a membranum. So was the scraped hide of parchment; as Isidore of Seville explained in the seventh century, ‘because the kings of Pergamum lacked papyrus sheets, they first had the idea of using skins . . . These are also called membrana because they are stripped from the members of livestock.’
Membrana enclosed the body; they also blocked its apertures, repelling foreign insinuations. Sound bounced off the ear’s membranum tympani. In Tudor England – as the playwright Ben Jonson described – Catholic continentals conspired in vain against the Protestant membrane that guarded the Virgin Queen cult: Elizabeth I ‘had a membrana on her, which made her incapable of man, though for her delight she tryed many . . . ther was a French chirurgion who took in hand to cut it, yett fear stayed her, and his death.’
In later times, however, membranes became porous, and it was science that made them so. In 1826, Henri Dutrochet wrote excitedly about a new discovery, osmosis, which he had demonstrated by making differently concentrated fluids pass through a chicken intestine. ‘At the outset,’ he recalled, ‘the specific objective of this work was to study the movement of sap in plants . . . This discovery led me much further than I had ever imagined. Indeed, in finding the mechanism and the cause of the movement of sap, I discovered the secret mechanism of vital movement [which belongs] equally to animals and plants.’ So clear was it to Dutrochet that osmosis provided a physical explanation for life’s mystery that he had to insist it was merely the immediate cause, and his faith in the ultimate cause – God – remained intact. But subsequent discoveries only vindicated his scientific awe. Under the microscope, the surface of tissues and fibres presented a marvellous array of ports and tunnels through which essential substances were exchanged. The twentieth century then unlocked the workings of life’s fundamental unit – the cell – which was wrapped in an intricate double-layered membrane studded with protein hatches for moving molecules in and out. These movements created electrical and chemical gradients between cells – and life energy, it seemed, was nothing more than the resulting force field of currents and flows. Dutrochet was right: the secret of life was to be found in membranes, whose miraculous architecture allowed them to selectively absorb and repel.
Absorption and repulsion. No principles can be more fundamental than these. They arouse our greatest passions – and our greatest poems; societies brawl over their priority. We cherish communion, exchange and intercourse, of course, but also distance, seclusion and defence. Talk of membranes, therefore, is never entirely literal. If one era sees skin as an impenetrable shield, while another admires its permeability, the reason may lie in allegory.
In Spheres, his vast meditation on contemporary life, philosopher Peter Sloterdijk supposes that the European psyche took its modern form when the protective membrane of the celestial sphere disappeared. The Ptolemaic bubble burst, and the planet drifted, shell-less, in empty space. But human beings need to be insulated from the terror of meaninglessness; and if the modern era has resounded so with the din of construction, it is because all its overwrought energies have poured into replacing the shattered cosmic housing. We fend off exposure, most conspicuously, by mastering and domesticating the one sphere remaining to us, until the earth itself is turned into a giant security system of information, machines, markets and nations. But no matter how physical and solid these structures appear, their function is symbolic – and symbols may wear out, even while the material world remains pretty much unchanged. At moments of transition or crisis, our fabricated metaphysical shelters can shatter, and we are naked again.
Perhaps we are at such a moment today. The concentric spheres insulating much of the modern world appear to be ruptured, suddenly; alien forces seem to be flooding in. We are preoccupied by national borders, whose skin seems flimsy in the face of contemporary flows of money and people. The perimeters of the self are breached by computer incursions: privacy disappears, so does the uncluttered mind, and even the boundary between human and machine. The division between human and nature, meanwhile, is tragically trampled: the latter is overwhelmed, and the modern world’s most cherished layer of security and consolation is lost. The planetary sphere itself turns against us: layers of the atmosphere are punctured, while rising sea levels overwhelm the previously secure outlines of islands and continents.
In such a moment, it is understandable that our fantasies turn sclerotic. Tiny infringements produce disproportionate outrage, because everything is at stake; we fixate on the reinforcement of fences, firewalls, valves, dams, checkpoints, tariffs, personal boundaries, restraining orders, visa regimes, customs inspectorates, inoculation procedures, quarantine facilities and so on. Individuals make use of defences once employed only by specialist institutions: surveillance systems, background checks, surgical gloves. They arm themselves against the threat that is everyone else, sharpening their own edges, carrying weapons and masks, researching how to identify ‘toxic people’.
Yes, it is understandable. But thickened membranes that let nothing through are also fatal. That is why it is so urgent that our response is not to harden, but to reconceive. And the job does not belong to mere governments, lawyers and technology firms. The protections we seek are imaginary and spiritual. Poets and philosophers must show us the way.