Derek Parfit's Teleporter Kills the Passenger

Derek Parfit introduced his teleporter in Reasons and Persons, published by Oxford University Press in 1984. The device works perfectly: it scans your body down to the atomic level, transmits the information, and assembles an exact copy at the destination. The original is destroyed in the scanning process.

Is the person who steps out of the teleporter you?

Parfit thought the question was less important than it seems — and that realizing this was a kind of philosophical therapy. The copy has your memories, your personality, your beliefs, your continuous first-person sense of being the person who stepped in. In every functional sense the story continues. But there is no thread of identity in the metaphysical sense that runs through the destruction and reconstruction.

His move was to argue that personal identity — the strict fact of whether you continue — is not what makes survival matter. What matters is psychological continuity and connectedness: overlapping chains of memories, intentions, beliefs, and character. These can be had in full by the copy. They can also be had in degrees, which is why Parfit thought our concern for our future selves was more like concern for a close relative than concern for exactly the same person.

The practical stakes are real. If Parfit is right, the fear of being destroyed in the teleporter collapses into the fear of death — and the fear of death itself looks different under his analysis. He argued in interviews that giving up the belief in a separately existing self made him feel less bounded, more connected to others, and less anxious about his own mortality.

Parfit died in January 2017. He had been working on the problem of personal identity for over forty years.