Are phenomenological essences the case in every world? I believe they are a priori, but are they necessary and immutable? A stock example of an essence is the extension of white.
We seem to experience essences, there is something it is like for colours to have extension, just as there's something it is like to experience colour. Is that right?
It seems strange to claim that a quale, an experience, is part of the structure of every possible world. Wouldn't that mean that some experience or other necessarily occurs? Or is it just wrong to say that logically necessary things must "occur"?