Second person knowledge and reciprocal interaction

A number of philosophers have posited a special “second-person knowledge”, expressible by phrases like “Bob and Alice know each other”. It is often claims that second-person knowledge requires reciprocal interpersonal interaction.

I think this is false. Suppose Alice and Bob live on Earth but have not yet had any interaction. There is a Twin Earth, where by chance everything happens like on Earth, and there are Twin-Alice and Twin-Bob there. Suddenly Earth and Twin-Earth diverge, as follows.

• Twin-Alice and Twin-Bob are teleported away for a vacation on another planet. They don’t enter into our story after this.

• Bob is teleported to Twin-Earth, where he takes the place of Twin-Bob, without noticing anything being different.

• On Earth, Bob is replaced by Robo-Bob, who is a robot who looks just like Bob, but operates on non-intelligent software that generates random human-like behavior.

• On Twin-Earth, Twin-Alice is replaced by Robo-Alice, who looks just like Alice, but operates on non-intelligent software that generates random human-like behavior.

• On Earth, Alice meets Robo-Bob, and they have what to all appearances is a reciprocal interpersonal relationship of the sort that generates mutual second-person knowledge.

• On Twin-Earth, Bob meets Robo-Alice, and they have a similar “relationship”, with Bob behaving normally for his character.

• In these “relationships”, the behavior of Alice and Bob is such that it would be normal for them (given their respective characters) in the context of a normal interpersonal relationships.

At this point, Alice and Bob think that the above “relationships” yield second-person knowledge, but they don’t, because these relationships are with a randomly behaving non-intelligent robot. Let’s add this:

• By chance, on Earth, Robo-Bob happens to behave just like Bob behaves on Twin-Earth.

• By chance, on Twin-Earth, Robo-Alice happens to behave just like Alice behaves on Earth.

Still, Alice and Bob don’t have second-person knowledge in virtue of the “relationships” with robots. For one, they don’t even know with whom that relationship would be. But there is a way in which they have something like Gettiered second-person knowledge with an unknown person. Finally, one more thing happens, a big reveal.

• Alice and Bob are informed of everything that happened above, and they are given knowledge of who the real Alice and Bob are, say by being shown genuine properly labeled photographs of one another.

At this point, I think a case can be made that Alice’s knowledge of Bob is sufficiently close to the kind of knowledge that she would have had if she had been interacting with Bob rather than Robo-Bob. Alice might say: “Since I know that the real Bob was behaving to Robo-Alice just as Robo-Bob was behaving to me, while Robo-Alice was responding to Bob just as I was to Robo-Bob, and both persons were behaving in the normal way for their character, I know as much about Bob from Robo-Bob’s behavior as I would have had I had a normal relationship with Bob.” And Bob might say the same thing, mutatis mutandis.

But there was no reciprocity. Alice’s behavior does affect Bob once Bob learns that Alice behaved just like Robo-Alice, and Bob’s behavior does affect Alice once Alice learns about Bob’s actual behavior, but this is a pair of one-way interactions rather than reciprocal.

There are three things one might say here:

1. Alice and Bob have second-person knowledge of each other.

2. Alice and Bob don’t have second-person knowledge of each other, but what they have has all of the epistemic value of second-person knowledge.

3. There is something complex about interaction that I have a hard time putting my finger on that makes for a relevant difference.