Legal doctrine that boils down to "trust me bro" isn't even bad doctrine (it's not proper doctrine at all), but I think the comparison is still valid here, because both sentience/non-sentience and art/porn may just be fundamental category errors.

Perhaps we can't define a "partitioning" rule because no valid partition exists.

For consciousness/sentience, that's an incredibly tough a pill for most to swallow; it would mean calling into question more hundreds of years' worth (probably more) of philosophical thinking, all of which was constructed on the axiom that "sentience" is a single indivisible trait: you either have it or you don't.

If we find that "root dependency" was little more than wishful thinking all along, a whole slew of Enlightenment-era philosophy (and all the modern legal principles derived therefrom) suddenly fall apart unless we find some other suitable criterion that would shore them up (or we just collectively avert our attention and pretend the conflict doesn't exist, which is the route I expect many would prefer to take).

> a whole slew of Enlightenment-era philosophy (and all the modern legal principles derived therefrom) suddenly fall apart

I don't think that's true. Pretty much all legal constructs hold up just fine under game theory regardless of whether or not you consider the world to be deterministic and have absolutely nothing to do with consciousness or lack thereof. Also note that a deterministic world isn't an argument against consciousness.

"I know it when I see it" is a famous line from a SCOTUS case in the 60's