Most people know energy cannot be destroyed. Interestingly, there is also a rule in quantum mechanics that forbids the destruction of information. This principle, called unitarity, is often illustrated by the example of burning a book: though the book is burned, the information remains, though it would be hard to “read” a burned book. This principle ran into some trouble with black holes, which might be able to destroy information. My interest here is not with this dispute, but with the question of whether the indestructibility of information has any implications for immortality.
On the face of it, the indestructibility of information seems similar to the conservation of energy. Long ago, when I was an undergraduate, I first heard the argument that because of the conservation of energy, personal immortality must be real (or at least possible). The reasoning was that a person is energy, energy cannot be destroyed, so a person will exist forever. While this has some appeal, the problem is obvious: while energy is conserved, it need not be preserved in the same form. So even if a person is composed of energy, it does not follow that the energy remains the same person or even a person at all. David Hume argued that an indestructible or immortal substance (or energy) does not entail the immortality of a person. When discussing the possibility of immortality, he claims that nature uses substance like clay: shaping it into various forms, then reshaping the matter into new forms so that the same matter can successively make up the bodies of living creatures. By analogy, an immaterial substance could successively make up the minds of living creatures. The substance would not be created or destroyed; it would merely change form. However, the person would cease to be.
Prior to Hume, John Locke also noted a similar problem: even if, for example, you had the same soul (or energy) as Nestor, you would not be the same person as Nestor any more than you would be the same person as Nestor if, in an amazing coincidence, your body now contained all the atoms that once composed Nestor at a specific moment.
Hume and Locke seem to be right and the indestructibility of the stuff that makes up a person (be it body or soul) does not entail the immortality of the person. If a person is eaten by a bear, their matter and energy will continue to exist, but the person did not survive being eaten by the bear. If there is a soul, the mere continuance of the soul would also not seem to suffice for the person to continue to exist as the same person (although this can be argued). What is needed is the persistence of what makes up the person. This is usually taken to be something other than just stuff, be that stuff matter, energy, or ectoplasm. So, the conservation of energy does not entail personal immortality, but the conservation of information might (or might not).
Put a bit crudely, Locke took this something other to be memory: personal identity extends backwards as far as the memory extends. Since people clearly forget things, Locke did accept the possibility of memory loss. Being consistent in this matter, he accepted that the permanent loss of memory would result in a corresponding failure of identity. Crudely put, if a person truly did not and could never remember doing something, then she was not the person who did it.
While there are many problems with the memory account of personal identity, it suggests a path to immortality through the conservation of information. One approach would be to argue that since information is conserved, the person is conserved even after the death and dissolution of the body. Just like the burned book whose information still exists, the person’s information would still exist.
One obvious reply to this is that a person is an active being and not just a collection of information. To use a rather rough analogy, a person could be seen as being like a computer program and to be is to be running. Or, to use a more artistic analogy, like a play: while the script would persist after the final curtain, the play itself is over. As such, while the person’s information would be conserved, the person would cease to be. This sort of “information immortality” is similar to Spinoza’s view. While he denied personal immortality, he claimed that “the human mind cannot be absolutely destroyed with the body, but something of it remains which is eternal.” Spinoza, of course, seemed to believe that this should comfort people. Perhaps some comfort should be taken in the fact that one’s information will be conserved (barring an unfortunate encounter with a black hole).
However, people would probably be more comforted by a reason to believe in an afterlife. Fortunately, the conservation of information does provide at least a shot at an afterlife. If information is conserved and all there is to a person can be conserved as information, then a person could presumably be reconstructed after his death. For example, imagine a person, Laz, who died by an accident and was buried. The remains could, in theory, be dug up and the information about the body could be recovered. The body could, with suitably advanced technology, be reconstructed. The reconstructed brain could, in theory, have all the memories and such recovered and restored as well. This would be a technological resurrection in the flesh, and the person would seem to live again. Assuming that every piece of information was preserved, recovered and restored in the flesh it might be the same person, as if a moment had passed rather than, say, a thousand years. While sci-fi, the idea seems sound enough.
One potential problem is an old one for philosophers: if a person could be reconstructed from such information, she could also be duplicated from the same information. To use the obvious analogy, this would be like 3D printing from a data file, except what would be printed would be a person. Or, to use another analogy, it would be like reconstructing an old computer and reloading all the software. There would certainly not be any reason to wait until the person died, unless there was some sort of copyright or patent held by the person on herself that expired a certain time after her death. But since personal identity is supposed to be what distinguishes a person from all other things, it is not something that can be duplicated. There are, however, those who disagree with this.
In closing, I leave you with this: some day in the far future, you might find that you (or someone like you) have just been reprinted. In 3D, of course.