Because I sincerely do not. I have frankly no idea how sentience arises from non sentience. But it's a topic that really interests me.
But to me the big mystery is how animals have sensation at all to begin with. What gives rise to that is a greater mystery to me personally.
There are examples of people who have no ability to feel pain yet are still able to think. Now I wonder if they ever experience mental anguish.
Clearly most animals are less educated, and most are less intelligent, but non-sentient? That sounds like 200-year old claims that "when one steps on the tail of a cat, it does indeed protest loudly, but not because it feels anything or because it would be sentient, no, no, it protests merely due to selective pressure, programming reflex circuits, since other creatures would show compassion, or back off due to a potential reaction by the cat."
Anyone who has had a pet like a cat or a dog knows they are sentient... if we consider ourselves sentient.
