Those who have read
Little Fuzzy know that the book's climax hinges on a court trial to both determine whether the titular species is sentient, and also to come up with a general definition of sentience.
Recently,
a New York court tackled that question when it comes to chimpanzees. Should chimpanzees be considered sentient? Honestly, this is a question I'm conflicted on, though I think a good case can be made in general for better treatment of animals, as we're finding them to be more and more like us.