Optogenetics is a technique that uses light to control the activity of cells by inserting light-sensitive proteins into their membranes. When light of a particular wavelength strikes these proteins, they open or close the gates on the membranes, allowing ions to flow and the cell to fire or fall silent. This assertion is titillating enough to pause and wonder: how much of an impact can our environment play upon our gene expression? Revisiting the earlier philosophers who treated light, water, and earth not just as settings but as the very conditions of intelligibility and being. Parmenides considered light the medium of truth itself.

If light can be engineered to switch cells on and off in a laboratory, what is it already doing to us? Melanopsin-containing cells in the retina report the brightness and colour of our surroundings to the brain’s master clock, and that clock keeps time through genes such as PER2, which rise and fall with the day managing our circadian rhythm.

My mind moves immediately to the light we live inside now, the blue glow of screens, the flicker of LEDs, the omnipresent cell phones and to the emerging evidence that this ambient light is not passive. If light can shape gene expression, could the mass incorporation of digital tools, on the pretext of learning aids, accelerated overnight by COVID-19, produce the behavioural shifts we are seeing in students? The fatigue, the disengagement, the fractured attention may that be a response to a changed photic environment.

The architecture of life does not merely receive light; it emits it. Every living cell, in the quiet of its own metabolism,........

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