LIKE MOST OF US, BENJAMIN Franklin did not want to die. Late in his life he expressed the wish that some method of preserving corpses might be found that would allow them eventually to be resuscitated. "Having a very ardent desire to see and observe the state of America a hundred years hence," he wrote in 1773, "I should prefer to an ordinary death, being immersed with a few friends in a cask of Madeira, until that time, then to be recalled to life by the solar warmth of my dear country!"

Franklin may be dead, but his dream of bodily immortality isn’t. Right now, at life-extension foundations around the country, there are several dozen corpses lying submerged in vats not of Madeira but of liquid nitrogen (temperature: -320 degrees F). The fond hope is that scientific advances will permit the decedents to be resurrected one day–perhaps not in time for the turn of the millennium but certainly by the beginning of the twenty-second century, when those of us who failed to make such provisions for immortality will be dead and gone.

One of these cadavers, at least according to legend, is that of Walt Disney. He is said to have elected to have his entire body deep-frozen–a needlessly extravagant choice. As most philosophers will tell you, the real vehicle of personal identity is not the body but a mere three-pound component of it: the brain. Heeding this wisdom, hundreds of other people have made arrangements to have their heads cut off with chain saws immediately upon being declared dead and put in cryogenic suspension within earthquake-proof "cephalaria." This cheaper option is called "going neuro," as opposed to the whole-body approach. "Actually, we think of it as removing the body," says the magazine of the Alcor Life Extension Foundation in Scottsdale, Arizona.

Is all this anything more than a waste of liquid nitrogen? Freezing bodily tissue, it is true, damages each and every cell. But such damage could be repaired by an army of molecule-sized robots, just the sort of thing we’ll be seeing in the next century, thanks to the emerging field of nanotechnology (from nanos, Greek for "dwarf"). As for what to do with the thawed-out and reconditioned brains, that’s the easy part: Simply lodge them in a fresh body cloned from a bit of the decedent’s DNA. The newly resurrected person will of course notice a sharp experiential discontinuity but will be oblivious of the decades-long "biostatic coma" that has finally come to an end.

Should this resuscitation scheme be realized in the next century or so–and, given that each part of it is technologically plausible, who’s to say it won’t?–immortality still will not be assured to those who try it. One problem is that our brain cells, like all the other nonreproductive cells in the body, are genetically programmed to self-destruct in a finite time period [see Hypotheses, November 1998]. Freezing such cells has been shown to delay the onset of their suicide but not to eliminate it.

But let’s suppose, again plausibly, that geneticists eventually find a way to disable the suicide program encoded in the brain cells’ DNA. Although the cells would still wear down over time, this entropy could be corrected by nanotech robots. Then the brain would be essentially immortal. Yet it is still subject to the risk of being destroyed in an accident–the probability of which, given enough time, approaches 100 percent. Once the brain is vaporized, any hope for the persistence of personal identity would pretty much seem to vanish.

Unless, that is, there was a backup copy in some safe place. Now, not even the giddiest futurist is proposing that we will be able to build a perfect working replica of a given person’s brain any time soon. But this might not be necessary. The important thing about the brain is not the lump of spongy gray meat itself but the stream of mental life it supports. The psychological continuity that gives rise to personal identity is a matter of brain activities involving memory, belief, and desire–all of which, in theory, could be downloaded into a computer. The brain is, after all, a system that obeys physical laws, and any such system can be simulated by a sufficiently powerful computing device.

Once this software of personal identity is extracted from the brain, the possibilities are endless. Human minds could be implemented in "alternative hardware," such as robots. They could be faxed from one galaxy to another at the speed of light. The only real threat to immortality that would seem to remain would be the end of the universe itself–either through the "heat death" of eternal expansion or ultimate contraction into an apocalyptic Big Crunch. Remarkably, scientific believers in eternal life have both scenarios covered. For the former, Freeman Dyson, physicist at the Institute for Advanced Study, has imagined implanting our minds in interstellar dust clouds whose activities would slow as the universe expands, resulting in a stretched-out but still infinite series of "moments of consciousness." For the latter scenario, the physicist Frank Tipler has argued in The Physics of Immortality (Anchor, 1995) that the energy of the Big Crunch could be harnessed to provide infinite computational power in the last second–and hence subjectively infinite time, as mental state followed mental state at an ever more rapid clip.

If such prospects for eternal life seem inhuman–or worse, tedious–there are always the old sham ways to achieve immortality: through one’s children, through one’s work. Apparently those weren’t good enough for Ben Franklin or Walt Disney–or, for that matter, Woody Allen, who once sensibly said, "I don’t want to achieve immortality through my work. I want to achieve immortality through not dying."

JIM HOLT

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