Boundary Permeability = Exchange with the Environment
As a self-aware entity I can speculate about the existence of individual life without awareness but my speculation is irrelevant to developing a description of human existence because human beings are self-aware. Consciousness, awareness that we are aware, is for us the key factor that makes meaningful individuality possible. Consciousness is the primary factor in all human behavior and is in fact so omnipresent that we frequently ignore it in favor of concentration on the objects of awareness.
No experience can be separated from the basic condition that awareness of it is a precondition for its meaningful existence. Objectivity, in the sense of knowledge of a pure existence of the thing in its self entirely apart from consciousness, does not exist for human beings. All reality, from the human point of view, is subject / object reality. Science depends on observation, all relationships depend on awareness of self and other, business depends on choice and behavior which in turn depend on the existence of awareness as a precondition. Without awareness of our selves as individuals no human pursuit that has any meaning would exist, because without awareness knowledge of individuality can not arise.
Franklin Merrell-Wolff, the American mystic philosopher, has explored the existence of consciousness in a particularly deep and thoughtful way and developed a philosophical system that posits consciousness without an object as the ground of all reality. In his aphorisms on consciousness-without-an-object, number 9, 10, and 11, Merrell-Wolff declares that; "Consciousness of objects is the Universe.", "Consciousness of absence of objects is Nirvana.", and "Within Consciousness-without-an-object lie both the Universe and Nirvana, yet to Consciousness-without-an-object these two are the same."
I personally favor such views, no one has to be a mystic to appreciate the existence of awareness of our own individuality and the awareness of others as being central to human existence and therefore important to take into account when trying to create systems that help humans achieve their full potential as conscious entities existing in a living finite physical environment.
How individual or alone are we? One of the primary signals that we are separate and alone is the fact that we have physical boundaries like skin and cell walls. How alone is a cell? It has a boundary that separates it from every other cell in the body but cell membranes are permeable, they let some things into the cell from outside the cell, and they allow some things to leave the cell through the cell wall. There is water inside the cell membrane and water outside the cell membrane, the only differentiation relative to the water is the cell membrane. The structures that form on the inside of the cell wall also use and participate in the flow of the water across the semi-permeable membrane of the cell wall.
All separation from the surrounding environment for any particular structure seems to follow the same general pattern. The separated structures we see and animate, are constructed out of the material around them and don't have an existence independent from these materials. The life forms and self-definition, separation, we experience is real, and at the same time completely interdependent and intercommunicative with everything around it, or not separate in any absolute sense, not truly alone.
The central nervous system uses the water in the cell and outside of the cell and its Semi-permeable membranes to generate an electrical charge. That charge travels along the axon to dendrite provide routes for intercommunication within the brain interconnecting with other cells. The spinal cord interconnects the entire body through the afferent and efferent nerves. The circulatory system also connects the entire body via water and cells of various types. Connective tissue connects the various individual parts of the body together.
On the external boundary of the individual defined by skin, lung, digestive, olfactory, and visual cells the mouth, gut and anus connect the individual to water and food that becomes the contents of the cells within their membranes. The lungs connect the individual to the environment through air and the process of respiration. Air connects to the whole individual via the transformation of air into oxygen at the alveoli and the marvelous transport of water in the blood through the cell wall of the red blood cell. Air continuously connects the individual to the environment, each other, and other life forms.
Each individual is then also interconnected physically with each every other individual through atmosphere, water, soil, sunlight, plant and animal life. So even on the physical level of our existence we are clearly separate independent entities and we are so interconnected with each other and everything around us that we are a whole process of life that is fully shared and not individual in the exclusive sense at all.
Even at the level of the smallest structures that make up our universe distinctions between objects don't imply separation in an absolute sense. In quantum mechanics the principal called the quantum mechanics of a proper open system states, "There is no such thing as an isolated system, and all systems are open systems that experience varying degrees of interaction through their shared zero-flux surfaces." This is also true of human beings at the macro level, there is no such thing as an isolated individual person, cell, or living entity of any kind.
The paradox of individuality is that while it is irreducibly true it is not absolute. The non-individuality of the self is equally irreducible and not absolute.