The world in the most general sense is unique, and there is no "other" world, since the very idea of "anotherness" is a kind of union, and being different from each other means to have something in common, namely, the property of being different.
However, the world manifests itself as a universe of numerous individual things. This diversity is inherent in the world, being a level of its integrity. Every separate part of the world is virtually related to any other part, thus reflecting the whole world, representing it in that particular aspect.
That is, there is infinity of worlds that represent the same world; these multiple worlds are the positions of the same hierarchy, the hierarchical structures unfolded starting from a particular unit (the topmost element of the structure). All such worlds are identical, since every one of them comprises the whole Universe. However, they may look quite differently, and even be opposite to each other.
For instance, the world centered on me is different from the world unfolding for somebody else, and the two views may be utterly incompatible. Still, my world will necessarily comprise the other's view; otherwise it would not be complete. The ability to "model" the other's world within our own is one of the fundamental properties of reason, a consequence of definition as universal mediation. As a conscious being I must be able to temporarily become anything at all, remaining myself as the unity of all these special models. The more reasonable I am, the deeper is my comprehension of the other.
Of course, such universality cannot be achieved in an instant, in a finite system. That is why, we must always exercise care while talking about "human" and "non-human", "conscious" and "non-conscious" forms of existence; the subject can take many unexpected forms, and, obviously, no person is entirely spiritual, combining all the levels of motion in an individual way.