[chadash]

I agree with most of this except for not having a definition of sentience. This is not a new topic and has been dealt with extensively in philosophy. I like a definition mentioned in a famous article Consider the Lobster by David Foster Wallace (a writer not a philosopher per se) where he proposes that a lobster is sentient if it has genuine preferences, as opposed to mere physiological responses. The question isn’t really definition but how to measure it.

[stormbrew]

This just falls into the same traps as anything else though. How do you know if the lobster has preferences? How do you know what you think are your own preferences aren't just extremely complicated physiological responses?

Everything I've ever seen on this feels far from conclusive, and it usually begs the question. You start from an assumption that humans have sentience, cherry pick some data points that fit the definition of sentience you're already comfortable with, usually including things we can't even know about any other entity's experience, and then say "huzzah, I have defined sentience and it clearly excludes everything that is not human!"

[wizofaus]

The "mirror test" isn't a bad place to start, and there are definitely animals that pass it that aren't human. But trying convincing dog-lovers that their dogs aren't sentient... (Personally, I'm not sure - but I do suspect they at least have some subjective experience of the world, they "feel" emotions, and are aware of the boundary between themselves and the rest of the world. Apparently they've even tried to measure sentience in dogs via MRI scans etc., and supposedly couldn't distinguish them from humans).