While we all like to think of ourselves as unique individuals, quantum physics has long suggested that that notion is an illusion. One of the core tenets of Buddhism that puts it at odds with most other religions, particularly Abrahamic religions, is that there is no Self, no core or essential being that makes a person a person. Rather, people are more an amalgamation of thoughts and sense impressions. Our awareness or consciousness (to use a loaded term) of these is generic and indistinguishable from that of others. Thus, all supposed marks of our individuality are really part of the world and not the self. The sense we have of the Self and a unique and individual existence, therefore, is a psychological trick of our brain, a way of integrating thoughts and beliefs into a whole Self in the same way that our muscles, bones, and sinews integrate an amalgam of cells into a whole body.
Quantum mechanics appears to support this idea in that particles do not have individuality but are in fact indistinguishable except by their properties. While classical statistics regards particles as individuals, quantum statistics does not. Take an electron and replace it with another electron and you can’t tell the difference. This so-called Indistinguishability Postulate lies at the heart of quantum statistics.
The more fundamental quantum field theory goes further than QM and takes away the very concept of particles and instead simply creates a “yes/no” statistics where a yes at a location indicates a particle is there and a no at a location indicates no particle (or what we call virtual particles). The field is one whole with one nature and identity is subsumed in its field distribution.
This is not unlike the Hindu notion of divinity. All are God. God is all and our individuality is like a yes/no in the field of the divine. This is in contrast to the clear distinction made in Western religions between God and human beings. In those religions, human beings are given individuality by God as they are made from “dust” (the better translation might be “soil”) rather than having their individuality by virtue of their own divine nature. Thus, we are beings of dirt whose identity and individuality comes from the spirit of the divine breathed into us from without.
Notwithstanding God’s opinion on the matter, we may ask if individuality is essential to our nature at all. Drawing on an alternative philosophy that is both ancient and postmodernist, quantum particles may not have any intrinsic identity at all, but human beings confer their identity to them by means of naming. Thus, by naming a particle as having a particular set of properties (for certainly the electron has no notion of the properties that human beings have chosen to measure), the experimenter, like a god, gives extrinsic identity to the particle in their detector.
Likewise, by means of naming, human beings confer identity on one another and, as social beings, we absorb that sense of identity. This socio-linguistic source of individuality has the advantage of not requiring the invention of a source of identity beyond the physical, but it has the disadvantage that it means that we are whatever other people say we are.
While it is clear that genetics and other physiological factors must also play a role here, none of these sources are, themselves, conferring any identity in themselves. Rather they inform us of how to “name” our own identity. Identity itself comes from the naming of those extrinsic and intrinsic factors. Language becomes key, therefore, in both quantum physics and human identity. For language, whether spoken or mathematical, describes what a particle or field or person even is and what might be considered part of its nature versus that of another. And indeed, the nature of that language: English, French, Chinese, or Hilbert-space operator theory, determines what kinds of identities can exist.
In the middle ages, this idea got the name nominalism: the idea that language was the basis for metaphysics (the theory of is-ness). Willem of Ockham and Peter Abelard were known to support these ideas. Buddhism can be thought of as a nominalist philosophy as well. Essentialist and neo-Platonist/Aristotelian philosophers such as Thomas Aquinas hated it.
If you are a Platonist and believe that there is a “world of forms” or a Thomist (one who derives their philosophy from Thomas Aquinas) and believe the forms exist within the mind or spirit of God, you imagine this-ness (primitive identity that is not dependent on property) existing separately from reality. For in the “real” world, we find no source of thisness.
Yet, even here there is question as to where there is individuality. Aquinas believed the soul was the Platonic form of the body. Thus, each and every one of us has a unique form. Plato, however, suggested that every instance of a thing had a form or template in some other world. Do electrons, lacking Aquinine souls, have a Platonic form? Or is it that the field in which they exist is a kind of universal form for electroness both within the world and yet standing apart from it? If so, then individuality may not be as important as the this-ness conferred by quantum fields. Thus, our own identity and sense of self is no more than a “yes” in the quantum field(s) that generates our existence.
In that case, quantum field theory may at once give us an essential identity and take it away for we cannot distinguish ourselves from others, existing, rather, within a universe-size quantum field that confers our is-ness.
Irrespective of our consciousness of our own existence, our nature may be essential, but if so then there is no scientific way to determine that. Moreover whatever that is is likely far more primitive than what we would like to be unique about ourselves.
Our identity is, psychologically, a function of our brain which develops its identity through development and the interplay of genetics, environment, language, and circumstances. Any self beyond that seems to be a matter of faith.
French, Steven, “Identity and Individuality in Quantum Theory”, The Stanford Encyclopedia of Philosophy (Winter 2019 Edition), Edward N. Zalta (ed.), URL = <https://plato.stanford.edu/archives/win2019/entries/qt-idind/>