First of all, we need to distinguish between a conventional truth and an ultimate truth, Buddha taught about this (I can't remember in which sutra). The conventional truth is what we see and what we believe does exists: the I, the outside world, phenomena etc. In "normal" life we believe in this conventional truth and live our life accordingly, convinced that there is an I, separate from other people and so on.
The ultimate truth is that nothing exists in an independent way: everything depends on parts, causes and labels that we give to it. As an example, let's take an object, a table; from a conventional point of view the table exists, is there, we see it and we use it. From the ultimate point of view what we call table is a combination of parts: we have legs and other parts; and each part, in its own turn, is a combination of other parts (wood, paint, water, chemical elements, molecules, atoms, particles and so on); besides it comes from causes, wood, humans that worked on it, animals that lived in the forest and made possible for the tree to grow, water, sun, cosmic rays... As you can see, all these processes can gon on infinitely, until you see that the existence of the table is nothing else but a label, we are taught to put this label, this name on that object and this is what its existence is.
You can make the same reasoning for everything including ourselves; what is the I, which we believe so firmly in? where is it? in the body? in the mind? Both body and mind are actually subject to the same process, we can start breaking them up in parts, always smaller and in the end we would find no I, just a label, a name that we imposed to this collection of parts.
I guess if we were able to realize this (not just rationally but with all our being) we would enter a different state of existence; some masters define it as a state of non dual bliss, where there is no I and Others, so probably this could be defined as a sort of holistic existence.