That said, I wonder if the claim can't be near-equivalently rephrased "it's impossible to imagine a non-reductionist scenario without populating it with your own arbitrary fictions".
Ah, that's very interesting. Now we're getting somewhere.
I don't think it has to be arbitrary. Couldn't the following scenario be the case?:
The universe is full of entities that experiments show reducible to fundamental elements with laws (say, quarks), or entities that induction + parsimony tells us ought to be reducible to fundamental elements (since these entities are made of quarks, we just haven't quite figured out the reduction of their emergent properties yet)... BUT there is one exception in this universe, a certain type of stuff whose behavior is quantifiable, yet not reducible to quarks. In fact, we have no reason to believe this certain type of stuff is even made of the fundamental stuff everything else seems to be. Every experiment would defy reducing this entity down to quarks, to the point that it would actually be against Occam's Razor to try and reduce this entity to quarks! It would be a type of dualism, I suppose. It's not a priori logically excluded, and it's not arbitrary.
I think we might separate the ideas that there's only one type of particle and that the world is reductionist. It is an open question as to whether everything can be reduced to a single fundamental thing (like strings) and it wouldn't be a logical impossibility to discover that there were two or three kinds of things interacting. (Or would it?)
Reductionism, as I understand it, is the idea that the higher levels are completely explained by (are completely determined by) the lower levels. Any fundamentally new type of particle found would just be added to w...
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