"When we try to pick out anything by itself, we find it hitched to everything else in the Universe."
No thing and no one exist “in themselves,” but only in relation to all other things. We are not neatly-separable objects, but knots of relations and contexts. And it’s in this sense that we literally call each other into existence.
I believe quantum physics demonstrates how deeply this view goes (that’s not to say our ancient predecessors anticipated it, of course). The fundamental discovery of quantum mechanics was that, upon isolating an electron from any other sub-atomic particle, you find the electron enters superposition. A superposition of positions is difficult to describe, but from what I understand, superposition is essentially to say that a particle is not in any particular position; a more extended wording would be that the electron is everywhere and nowhere — both and neither. Isolated from all other sub-atomic particles, the electron loses any particularity or uniqueness, instead becoming a wavefunction — a spectrum of possible positions, each as equally valid as the other.
This discovery, though odd, may seem inconsequential. Electrons are so small we can go a whole lifetime feeling as if we’re not interacting with them at all, even while being composed of them. And besides, one may add, even if electrons can enter superposition, that’s a reality entirely foreign to our own: I don’t exist in every possible place I could be — just here. So what’s so important about what happens at the Planck scale?
It was for this reason Erwin Schrödinger devised his famous thought experiment: Schrödinger’s cat. A cat would be placed in a box, hermetically sealed off from the rest of the world, with a vial of poison, hooked to a hammer meant to swing and shatter the vial. Whether the hammer would swing and break the vial, killing the cat, was entirely dependent upon a single atom — a radioactive isotope, threatening to decay. Should the atom decay completely, the hammer will swing, breaking the vial, killing the cat; if it does not decay, the hammer will not swing, leaving the cat alive.
Conventional wisdom says what we would presume to be obvious: either the atom decays and the cat dies, or else it doesn’t and the cat lives. But the logic of quantum mechanics adds an odd addendum: the electrons of that atom, being in superposition, are, in fact, in both states — at once decayed and not decayed. And both. And neither. So what of the cat? If the radioactive isotope is both decayed and not decayed, then does the hammer mechanism trigger or not? Does the cat live or die?
Niels Bohr’s Copenhagen interpretation of quantum mechanics answered that the whole system would remain in superposition unless an outside observer knocked the system out of superposition, into a singular position, through “observation” — a term neither Bohr nor his contemporaries felt much need to define. (As a side note, virtually no one in the scientific community accepts the Copenhagen interpretation any longer; that said, the New Age community has still had no problem clinging to it.) From this view, the wavefunction “collapses,” presumably randomly, into only one of its possible states — the state the observer would experience: either a dead cat or a living one. However, many physicists since Hugh Everett would suggest that the wavefunction, in fact, never collapses; the whole system remains in superposition, but we only experience one of those positions, while other versions of us would experience all other possible positions. You may happily find the cat still alive, but another you in a “parallel world” isn’t so fortuitous.
Regardless of one’s interpretation, I think Schrödinger’s point was to demonstrate that it matters a great deal to us “up here” what’s going on “down there”; the sub-atomic or Planck scale, in fact, determines what we experience on our own scale of reality. Thus it matters a great deal how we interpret Schrödinger’s cat.
Modern quantum physics, leaning more closely to Everett than Bohr, predicates itself on a relatively more recent discovery — quantum decoherence. As I mentioned above, an electron enters superposition only when hermetically sealed off from all other sub-atomic particles. However, this wasn’t discovered until near the end of the last century. Before, it was uncertain what put the electron in superposition and, therefore, what collapsed its wavefunction. The culprit is collision with other particles.
In superposition, an electron is in a state of coherence; as a wavefunction, we might compare it to an olive tree, a single trunk branching out in every possible direction. However, in our universe electrons are seldom if ever isolated — we find this proverbial tree in an orchard of sorts. Just as the branches of separate trees can be tangled with one another, various positions within the wavefunction of one electron can collide with other positions in the wavefunction of another electron. Each of these “collisions” is an instance of decoherence, when a wavefunction collapses, or even fragments, into a particular state. When two wavefunctions make contact and decohere, they split into individual states wherever they intersect — in short, multiple “worlds,” so to speak, are born.
The reason electrons typically aren’t in superposition is because they are in contact with something else: another electron, a photon or neutron, etc. But the electron-photon collision we experience is only one intersection between that electron and that photon’s respective wavefunctions; presumably there are other “worlds” accounting for every other possible intersection between those two wavefunctions. But the fact that we ourselves are experiencing any particular instance of an electron and photon making contact at all is because of that decoherence, that collision.
There’s an age-old question in philosophy, which I believe Leibniz expressed best: why is there anything at all rather than nothing? More precisely: why is there this particular arrangement of things, rather than some other arrangement, or nothing at all? Leibniz expressed this through his own concept of striving possibilities, of all possible worlds in contest with one another in striving to become actual, only the most perfect among them coming into existence. In a similar vein, Everett theorized that if we can describe electrons and other sub-atomic particles as wavefunctions, then perhaps we can describe the entire universe, itself composed of sub-atomic particles, as a universal wavefunction. The cosmic story would, therefore, go something like this: before our universe came into being, it existed in superposition — a spectrum of every possibility, in a state of coherence. Something disrupted that balanced state, decohering and collapsing the wavefunction into our particular universe, and possibly even others. But that decoherence, that splitting — like white light hitting a prism and splitting into a rainbow of colors, all contained within the light itself — occurs only by way of collision or interaction. This electron is only here because another sub-atomic particle was also there; this universe may also only exist because its other variants exist elsewhere, and vice versa.
An electron, without another sub-atomic particle to which it can relate, would exist in a kind of Platonic non-being — “coherent,” all possible states, and thus nothing in particular. It’s through interaction with other sub-atomic particles that it develops anything like particularity, uniqueness. In a very real way, the electron does not exist in itself, but only in interaction with and relation to other sub-atomic particles.
By way of analogy, our own lives are metaphorically and quite literally like quantum decoherence. From the Planck-scale upward, we are bundles of sub-atomic particles ourselves, and thus the result of countless collisions between wavefunctions. And as our particular universe exists only in relation to all other variants of itself, we too exist in our own particularity because of the existence of other possible variants of ourselves.
Similarly, on a more familiar scale, we’re born with twice as many neurons as we’ll need in our lives; as that count diminishes, we slowly move from a analogical superposition of possibilities in infancy to the particularity of adulthood. Further, we find ourselves entirely embedded in time and space, deriving ourselves from that collision. For example, I am not simply 25 years old, but the 25 years beginning on 11 October 1993 till now (with hopefully many more years ahead). Moreover, I’m not simply 25 years of age from 11 October 1993 to now, but from around 2 PM in Spring, Texas on 11 October 1993 till now, born to particular people who in turn exist in relation to particular dates and locations. I’m not simply time or space, but the particular stream of time beginning in that particular place, moving through particular other places, from which I cannot be untangled. There is no “me” outside these places and times. Moreover, I’m not simply the sum of my choices, as if I could have made those choices anywhere and at any time, but I am the sum of all my interactions at particular times with particular people, under particular circumstances. There is no “me” that does not also come with the times and places I’ve experienced, all the people I’ve met, and with whom I’ve interacted. I am no island unto myself, but one part of a vast network of interactions, collisions which decohere and pull me from a vague superposition into the specificity of who I am at this very second.
And the same goes for you, and everyone you’ve ever encountered, or may encounter. We are not pieces on a chess board, neatly separable from the board itself; we are like waves, entirely non-existent apart from the surfaces and mediums we run along. Thus more mystic or contemplative traditions suggest that the ego — our sense of being neatly separable from our experiences, environments, and timelines — is an illusion. There is no “you” that didn’t go through what you’ve experienced, because those experiences shaped you — they are you, and you are them. And thus contemplatives say that you are not a separate agent having an experience, but that you are the experience itself. You are not hearing a separate noise — you are the hearing. You are not seeing a separate object — you are the seeing. You are not sitting in a chair — you are the sitting in the chair. You and I are not interacting — we are the interaction.
Rather than springing from a singular governing force, which rules us of its own volition; and rather than simply “coming into the world” like an intruder or foreign agent; we are a part of a vast network of mutually-sustaining components. We are not neatly separable objects, but knots of context and relations. Life is a web, always already entangled, each shaping the other, each calling the other into existence.
Nothing and no one exists in themselves, only in relation to the other — as relation itself.
Hugh Everett, "The Theory of the Universal Wavefunction,” Manuscript (1973), 3–140 of Bryce DeWitt, R. Neill Graham, eds, The Many-Worlds Interpretation of Quantum Mechanics, Princeton Series in Physics, Princeton University Press
Michael Epperson, Quantum Mechanics and the Philosophy of Alfred North Whitehead (Fordham University Press, 2018)