Roadside Picnic: An Alien Walks into a Bar
Let’s put it this way. A man meets an alien. How does each figure out that the other is intelligent?” “No idea,” Valentine said merrily. “All I’ve read on the subject reduces to a vicious circle. If they are capable of contact, then they are intelligent. And conversely, if they are intelligent, then they are capable of contact. And in general: if an alien creature has the honor of being psychologically human, then it’s intelligent. That’s how it is, Richard. Read Vonnegut?”