‘Infra-thin’ (French inframince) is a concept developed by Marcel Duchamp to connote a distance or a difference between two things—a separation that cannot be perceived only imagined. Duchamp described it as “the warmth of a seat which has just been left” or the “reflection of a mirror.” Duchamp said he “believed that by means of the infra-thin one can pass from the second to the third dimension.” For Duchamp, passing from the third to the fourth dimension was not a thought exercise about time and relativity theory. He thought of the infra-thin as representing a space beyond the world of solid things and beings—higher modes outside our ordinary experience.
Like the reflection of a mirror, the space between the surface and the bottom of a lake is infrathin. It is that in-between space where you can see one or the other but not both at the same time. They co-exist but by inference only. The depth of the lake is visible through the surface only when the eyes focus beyond the reflecting images of high trees and sky that morph along the interplay of photons on our sense of seeing. John Ruskin explained that we see the reflections above and below but “we cannot tell, when we look at them and for them, what they mean.”
We tend to take in both the surface and the depth at the same time, but that is artificial. It is the way I go through life, taking in the propaganda on the TV, convincing myself I am empathetic to the suffering of others—but I don’t actually see them below the surface. To do so would require that I let go of my comforts and travel to that in-between zone just below the surface, like a rite of passage to an existential place. It involves some sort of personal transformation, which follows the horrifying disorientation that precedes self-understanding.
My habit is to remain on the surface, neither moved by an increasing loss of civil liberties and pending environmental calamities nor contemplating the metaphysical possibilities of compassion. That in-between state is for those of us unable to make a complete transition so we remain apathetic while we fossilize and disappear into the infra-thin beyond the horizon of time. Perhaps a more intelligent species will discover our remains and sigh in what will be remembered as the human Age of Loneliness.
According to George Monbiot, the Age of Loneliness is killing us. Collectively, human beings will have to emerge from the view that Earth is something to be consumed and the belief that we are all in competition with each other. The in-between state is the chaos we will experience when or if we confront the system and come together with a new vision—one that looks above the surface and towards an expanded reality where we learn to respect and care for Nature and all Her inhabitants. It requires that we all focus on what makes us human in the first place—our natural state of bonding and connecting. In that state, the infra-thin warmth we leave for future generations will be love.
 Marcel Duchamp, Notes (G. K. Hall 1983), p. 45
 The Writings of Marcel Duchamp (DA Capo Press 1973), p. 194
 John Ruskin, Selected Writings (Oxford University Press 2009), p. 8
 Edward O. Wilson, Beware the Age of Loneliness, The Economist; Nov 18, 2013.
 George Monbiot, The Age of Loneliness is Killing Us, The Guardian; Oct 14, 2014.