Counterpart Theory

Let’s assume the many-worlds interpretation to quantum mechanics. What the mad philosopher David Lewis called “the plurality of worlds.” Where abstract modal propositions are reduced to quantifications over a set of non-concrete possible worlds. Where “actual” is just an indexical term, referring to the world we inhabit.

The most interesting consequence of this theory, beyond the bizarre ontology, is that of our theoretical counterparts. Each object in the actual world would have an infinite number of counterparts across all the non-actual worlds. The question then is this: what should our attitude to our counterparts be?

Obviously direct communication between counterparts is impossible. There can’t be any kind of interaction between an actual and non-actual object. But this doesn’t necessarily rule out indirect communication. After all, from an infinite set of possibilities we can infer any possible consequence.

With that in mind, let’s try a thought experiment.

Imagine that you’re going to communicate with the counterpart of yourself in a possible world. How would you begin? Perhaps “Hello, are you there?” Obviously you shouldn’t expect any kind of response. That would be mad.

But imagine instead that you’re the one receiving this interworld message. If there are an infinite number of ‘you’s’ out there, there’s bound to be a subset of them that are also currently engaging in the exact same thought experiment you are. Your role then is at once both broadcaster and receiver.

So another version of you has sent you a message “Hello, are you there?” How will you respond? Maybe “Yes, I can hear you. How’s it going?” Again, you broadcast this message out into the ether of non-possibilities.

Although you are in fact only really communicating with yourself, it does follow that you’re also interfacing with an infinite number of non-actual counterparts. What seems like a metaphysical impossibility is actually possible. It’s at once both completely uninteresting and utterly fascinating.

You are not alone.