We're the only species on the planet that knows what they are. We've only known it for a century or so- because we developed science. And we developed science after we'd first developed religion and government and reading and writing. We know what we are. Dogs don't know they're dogs.
Dogs know who their rivals are, they know what to mate with, roughly speaking.
Sometimes they don't seem to when they go after your leg. And that's actually a sort of good measure of how crude their discrimination capacities are. They have a few simple rules and they're just born knowing those rules. They don't really understand them. At some point, we say, this is just a silly hypothesis.