Though particle physicists cannot claim with certainty to have identified a truly elemental particle, I believe I am more than qualified to speak with profound authority on the subject because I am one, and so are you.
"Cogito ergo sum." (Descartes)
I think, therefore I am. Certainly one must exist in order to experience, and the fact that you experience is convincing proof you exist.
You ostensibly consider yourself to be an existence, else you would call yourself "we" instead of "I". But what exactly is an existence?
Since the time of Democritus of Abdera (460-370 BC) it has been postulated the Universe is comprised of particles which - though they may be profoundly minute in nature - are not infinitely divisible. It is inherently logical that before the smallest non-empty set can be assembled, there must exist an individual element with which the set may be populated, a single existence that is not composed of independent parts, an irreducible physical manifestation consisting only of itself. I call this elemental identity an 'entity'. So far, physicists haven't been able to find a truly verifiable entity and it is entirely possible they would not recognize one even if they could isolate it.
The material objects with which we interact in our environment are composites. A chair, for example, is the label we use to conveniently describe a set of parts including a seat, legs, back and arms. If its construction is of wood, then those parts are made of sets labeled 'cells' which are comprised of sets labeled 'molecules' which are, in turn, formed by sets labeled 'atoms', whose protons, neutrons and electrons have been theoretically superseded as fundamental particles by hadron groups populated by even smaller sub-sets of quark and lepton particles and anti particles which, themselves, may or may not be truly irreducible.
An irreducible physical entity is an existence. Everything comprised of those entities, from a proton to a galaxy cluster, is a composite. An existence is not a composite and a composite - even though it may have a unique label - is not an existence; they are two mutually exclusive sets, one which by definition must be limited to a single element versus one which must not.
Your body is a composite - a collection of billions of separate elements or fundamental particles, each with its own individual properties. Each basic particle pre-existed your birth and will ultimately survive your demise. Each has a unique history, a separate location and physical domain. Logically this is a conundrum. How can you be an existence if that manifestation which you consider to be yourself is a composite? A collection of particles would have as many separate, individual properties, histories and identities as there are elements in the set.
The Pinocchio Hypothesis
To reconcile this disparity, hordes of scholarly pundits with names basking in beakers of alphabet soup profess that if you toss just the right combination of terrestrial ingredients into a primordial cauldron and stir it really, really hard for a very, very long time, you can produce a composite that thinks, propagates and experiences a single existence with an individual identity. That may sound silly (I call it the Pinocchio hypothesis), but which lowly layman in his right mind would dare contradict an entire horde of scholarly pundits - especially when they are basking in beakers of alphabet soup. So, with an eye of newt and wing of bat, a pinch of this and a dash of that, these pundits explain away this egregious departure from logic by imbuing a common natural phenomenon called emergent properties (EP) with extra, more mystical powers, permitting them to cite biochemical evolution as the exclusive source of all life on Earth.
But even the most tenured of scholars aren't able to explain the specific mechanics of EP that transform a person with 8x1027 atoms into a single existence with an individual identity. In fact, there seems to be two distinct factions in the EP camp. The 'integration' group assures us without hesitation that some unknown power of unification melds a composite into a single identity and awareness. This faction tells us 8x1027 = 1. On the other hand, the 'emergence' group tries to convince us 8x1027 = 8x1027+1, claiming any sense of self is due to the whole being greater than the sum of its parts. They expect us to believe composites can conjure up a supervening entity, a temporary ego or virtual being with its own separate awareness and identity. In their practice of this mathematical sorcery, proponents of EP have been idiomatically reduced to casting the incantations "integrated" and "emergent" because "abracadabra" and "hocus pocus" are currently shunned and disfavored by the orthodox scientific community.
Hogwarts! If this is science, then Harry Potter is the next Isaac Newton. If you believe you are the corporal product of emergent properties then you are claiming that you are an occurrence and not an existence. Merlin, himself, would have been embarrassed by such magical thinking.
So what is life?
To quote Sir Arthur Conan Doyle's famous character Sherlock Holmes, Chapter 6 'The Sign of Four', "when you've eliminated the impossible, whatever remains, however improbable, must be the truth." Life is no chemical accident, nor was it conjured into fruition by some benevolent and omnipotent deity. Life is simply the product of a spectrum of undiscovered entities, irreducible elements with the attribute of natural animation that long ago began to manipulate the resources of this planet or 'wear the mud' so to speak. Some call them "souls", others call them "spirits" or "life forces".
Our physical size is extremely tiny prior to our trek into life (a feature for which anyone who is, was, or ever will become pregnant can be eternally grateful), so it comes as no surprise that we haven't been able to isolate and identify that element within us that compiles and compels our corporal garb. Your body is something you wear not something you are. It does; however, seem to be a necessary tool in order for us to function and think in human terms. By rote and repetition you have been trained since birth to think you are that thing you see in the mirror - hair, eyes, nose, skin, and appendages. You have developed the self-image that your body is YOU. But your corpse is, in fact, entirely removable - demonstrably so. If you cut off an appendage, it will suddenly be over there, yet you will not lose your identity. You will probably still have feeling in a phantom limb that isn't there. Just because something was held onto your corpse by molecular bond didn't make it YOU. Your body is simply the remnants of that hamburger and fries you ate a few years ago, that beer you had yesterday and that delicious Cesar salad from the 1990's. Most of the cells you wear today will be replaced by new cuisine within the next seven years or so. The brain is said to be the home of the id, yet you can remove any number of its lobes and still retain your identity; there is no specific cell in your entire corporal structure whose removal would cause you significant distress, much less destroy your sense of self.
As strange as it may seem, you have no idea what you actually look like because consciousness, as we know it, only occurs when you are wrapped within your corporal shell. Even if you could strip away the blood and the bones just long enough to glimpse your true countenance, you might see nothing at all, for that fundamental element which is you may not have the property of mass. Like space, your essence may be transparent - more invisible than the air you breathe.
Centuries or eons from now when the first soul or life force is detected by a technology not yet envisioned, some interesting questions will undoubtedly arise -
* Are all life forms fungible? Does the spirit of a plant or bacterium differ in its basic nature from an insect, a fish, a bird, a mammal? Am I a human only due to the "luck of the draw"?
* At what point is the soul 'encorporated'. Is it introduced by the sperm? Is it resident in the ovum? Is it assimilated after conception?
* Does it have a fixed volume or does it expand and contract? Does it grow as it grows the body or does it just weave thin fibers of itself throughout the nervous system?
* If my life force can be tracked to another life cycle, can I take it ($$$) with me??
* When the Earth was formed, were the different spirits already embedded in the cosmic cloud or did they arrive over time from other areas of our galaxy ... or beyond?
* How did we get here? Why did all life in the solar system seem to congregate about this planet? Is it possible our essence can propel itself through space to select a suitable environment?
* How many souls are there in the region of Earth? Are others arriving? Do some leave?
* Where was I fifty trillion years ago? Where will I be fifty trillion years from now?
* Will there still be taxes? Will bureaucrats still govern the world?
Life and death are physical conditions, transient states of being. Existence is eternal. When you die you will be dead - but you will still be. There will come a time in the history of mankind when future societies will look back upon our modern era and wonder how creatures who couldn't even understand the nature of their own being could have considered themselves intelligent when the evidence that surrounded them was so obvious and compelling.