To agree with a previous reply:
There are no two identical entities in the universe. If there were then how could they be differentiated?
If one considers the current popular theory of the origin of the universe - the "big bang" theory - the implication of this theory is that all matter was inextriably linked while expanding from a singularity.
If one applies the concept of uniqueness then it follows that, for example, there is only one quark which is present throughout the observable universe in a multidude of states.
An analogy is the use of mirrors to amplify a light source: it is the same photon at different times, but to a slow observer appears to accumulate in the same way that a point source, a star, becomes a line during a long exposure of a camera.
On this basis, the entire universe is a reverberation of a single note reflected and re-reflected through time.
If there is is only one of anything then this simplifies the theories somewhat.
However this concept allows "action at a distance" (a result of the point origin of the universe) and other consequences which affects fundamental concepts such as the conservation of energy (If the entire universe is involved in interactions then conservation of energy becomes meaningless because each interaction is conserved across the entire universe).
All of the above is pure speculation, no experimental proof, so comes into the category of conjecture, not science.