I reject philosophies of immanence, not because they are demonstrably incoherent or false (yet), but because they foreclose questions about ultimate meaning rather than being open to addressing them in a perhaps non-discursive way.   To postulate that there is only one world and that it is made up solely of relations 'internal' to it is to fail to make contact with mystical questions on the one hand and questions around philosophy of science and mathematics on the other.  

It is more rational to suppose that the basic 4-world map provided by most cosmologies across cultures is basically accurate, to use this as a starting point and then to look closely at the nature of each world in light of modern developments in science and art.   Thus we have the nomination of the Four Alimonies:  OIOION, ANANON, YLYLCYN, S/HE/YM/N

However the burden falls to the tetrad-affirming thinker to explain why there are four worlds.   This is where Plotinus's theory of procession and return is helpful.  Each world has a sort of internal nature and an external nature - a naturans and a naturata.   But there is a principle generating multiplicity from this - because what is generated as naturata, or what proceeds, turns back around and attempts to re-create that which generated it - but fails to.   This is the basic tragedy of existence.  Comparisons can be made to the death drive and to the logic of representation - but we don't necessarily need to invoke modern concepts to support this.  We can simply name it.  Thus it has two names:  Kel Valhaal and Reign Array