A thought experiment

In 1984 the philosopher Derek Parfit suggested a thought experiment dealing with the nature of individual consciousness. According to my admittedly imperfect memory he imagines a teleportation machine that works by "scanning" an object. As it scans the object atom by atom, it destroys the atom by turning it into energy. It sends the energy to a receiver which uses the energy to create an identical atom in a different location.

The item is thus destroyed at the original location to be rebuilt a distance away. So far, so good. The item is re-assembled, atom by atom, to form an identical replica of the original item. Since the replica is in every sense identical, can one say that the replica IS the original item? One assumes that an operating machine would be disassembled and reassembled, still working, at the different location.

Now, thinking of the human as an extremely complex machine, we suppose the device "sends" a particular person through the intervening space to the receiver where the person steps out of the receiver. Whatever thoughts the person was thinking at the time of the transmission would continue to be thought when the person was reassembled. Is it the same or a different person? Parfit then suggests a problem: suppose that due to a malfunction, the original is NOT destroyed. Which of the absolutely identical copies can be said to be the original?

Of course the issue of identity and how it can be defined is the concern here. But I want to suggest an interesting variant: suppose the "original" is destroyed as is posited in the original concept. From the standpoint of the person who steps out of the receiver, his thought processes seem consistent and continuous from his birth to the present instant. He would certainly experience in his awareness that he was the actual person who stepped into the transmitter. But now imagine the experience of the original. He steps into the transmitter, and there he ceases to exist. His awareness stops, no matter that an identical awareness starts elsewhere. So while the person stepping from the receiver would experience a continuous and harmless process, the original consciousness would have ceased to exist because its atoms were destroyed.

What are we to make of this in defining individual consciousness and identity? The process is not symmetrical. From the standpoint of the person at the receiver, there has been no interruption. But from the standpoint of the sender, the process was discontinuous and terminal. We can of course never know this experience directly, since while the receiver person reports "No problem" or the equivalent, the person at the sending end has nothing to report and nothing to report with. In fact, this outcome cannot apparently be resolved by experiment since there can be no report of the sender's experience! What we have just considered here is the only evidence we are ever going to have.