Is our personal identity just the particular make up of our physical bodies at a particular point in time? And if so, would a teletransporter that replicated our physical bodies on Mars preserve our personal identity? Thought experiments and transhumanist sci-fi technological dreams such as this are deceptive means of doing philosophy and should be kept in Hollywood and marketing campaigns, writes Nicholas Agar. 

In his 1984 philosophical classic Reasons and Persons Derek Parfit tells a story about a fantastical futuristic technology – the Teletransporter. 

I enter the Teletransporter. I have been to Mars before, but only by the old method, a space-ship journey taking several weeks. This machine will send me at the speed of light. I merely have to press the green button. Like others, I am nervous. Will it work? I remind myself what I have been told to expect. When I press the button, I shall lose consciousness, and then wake up at what seems a moment later. In fact I shall have been unconscious for about an hour. The Scanner here on Earth will destroy my brain and body, while recording the exact states of all of my cells. It will then transmit this information by radio. Travelling at the speed of light, the message will take three minutes to reach the Replicator on Mars. This will then create, out of new matter, a brain and body exactly like mine. It will be in this body that I shall wake up.