Conal Elliott cites Steve Horne:

I look at this World parameter as purely hypothetical, a trick used to gain an intuition. Whereas Jerzy (I think) uses it to claim Haskell is referentially transparent - those differing x and y values come from different worlds, or different world-states.

I don't see this interpretation in Jerzy's words, and I'd be very surprised if he had that sort of argument in mind.

I don't think either having used the 'World' model as an argument of the referential transparency.
The main reason is that I don't know what does it mean, the referential transparency of the real world.

There is a philosophical issue involved: the problem of IDENTITY, which is as old as the humanity, and it will survive it... We simply don't know what does it mean: "the same"...

But I disagree quite strongly with the idea of "World parameter as purely hypothetical, a trick used to gain an intuition". I mentioned the language Clean (no reaction, seems that Haskellians continue to ignore it...)

In Clean this IS the IO model. You have such entities as FileSystem, which has the Unique Access property, etc. You can put all that in an equivalent of the IO Monad, constructed within Clean itself, not as a primitive.

Jerzy