[grishka]

One thing that sets humans and animals apart is language. The ability to transfer abstract thoughts and ideas between individuals.

Would you adopt an alien creature capable of reasoning and and expressing its thoughts as a pet? Or would you consider that enslavement?

[adrianN]

It's all a matter of degrees. My cat certainly is able to communicate with me and there are smarter animals around that we keep in captivity (e.g. dolphins).

[grishka]

There is a clear line between "the cat says meow and you figure out what it wants based on the context" and "someone thinks something and says it out loud such that you now have the same thought". It's this process of transfer of abstract thoughts between people, and later the ability to preserve those thoughts on paper, that made our civilization possible.

[adrianN]

So were is the line? Is an Ape using sign language on our side of the line, or on the cat's side? At what age does a child cross the line?

[grishka]

On the cat's side. They don't use it to represent abstract ideas.

I can describe to you something you've never seen and have no idea about, yet you'll be able to imagine it and reason about it from my description alone. Apes or dolphins or crows or dogs or other animals we consider smart can't do that. If they could do it, they'd have their own civilization by now. It's a uniquely human trait among all life forms we're aware of.